Encodings

The key to creating meaningful visualizations is to map properties of the data to visual properties in order to effectively communicate information. In Altair, this mapping of visual properties to data columns is referred to as an encoding, and is most often expressed through the Chart.encode() method.

For example, here we will visualize the cars dataset using four of the available encodings: x (the x-axis value), y (the y-axis value), color (the color of the marker), and shape (the shape of the point marker):

import altair as alt
from vega_datasets import data
cars = data.cars()

alt.Chart(cars).mark_point().encode(
    x='Horsepower',
    y='Miles_per_Gallon',
    color='Origin',
    shape='Origin'
)

For data specified as a DataFrame, Altair can automatically determine the correct data type for each encoding, and creates appropriate scales and legends to represent the data.

Encoding Channels

Altair provides a number of encoding channels that can be useful in different circumstances; the following table summarizes them:

Position Channels:

Channel	Altair Class	Description	Example
x	X	The x-axis value	Simple Scatter Plot with Tooltips
y	Y	The y-axis value	Simple Scatter Plot with Tooltips
x2	X2	Second x value for ranges	Gantt Chart
y2	Y2	Second y value for ranges	Candlestick Chart
longitude	Longitude	Longitude for geo charts	Locations of US Airports
latitude	Latitude	Latitude for geo charts	Locations of US Airports
longitude2	Longitude2	Second longitude value for ranges	Connections Among U.S. Airports Interactive
latitude2	Latitude2	Second latitude value for ranges	Connections Among U.S. Airports Interactive
xError	XError	The x-axis error value	N/A
yError	YError	The y-axis error value	N/A
xError2	XError2	The second x-axis error value	N/A
yError2	YError2	The second y-axis error value	N/A
theta	Theta	The start arc angle	Radial Chart
theta2	Theta2	The end arc angle (radian)	Pacman Chart

Mark Property Channels:

Channel	Altair Class	Description	Example
angle	Angle	The angle of the mark	Wind Vector Map
color	Color	The color of the mark	Simple Heatmap
fill	Fill	The fill for the mark	Ridgeline plot Example
fillopacity	FillOpacity	The opacity of the mark’s fill	N/A
opacity	Opacity	The opacity of the mark	Horizon Graph
radius	Radius	The radius or the mark	Radial Chart
shape	Shape	The shape of the mark	US Income by State: Wrapped Facet
size	Size	The size of the mark	Table Bubble Plot (Github Punch Card)
stroke	Stroke	The stroke of the mark	N/A
strokeDash	StrokeDash	The stroke dash style	Multi Series Line Chart
strokeOpacity	StrokeOpacity	The opacity of the line	N/A
strokeWidth	StrokeWidth	The width of the line	N/A

Text and Tooltip Channels:

Channel	Altair Class	Description	Example
text	Text	Text to use for the mark	Simple Scatter Plot with Labels
key	Key	–	N/A
tooltip	Tooltip	The tooltip value	Simple Scatter Plot with Tooltips

Hyperlink Channel:

Channel	Altair Class	Description	Example
href	Href	Hyperlink for points	Scatter Plot with Href

Level of Detail Channel:

Channel	Altair Class	Description	Example
detail	Detail	Additional property to group by	Ranged Dot Plot

Order Channel:

Channel	Altair Class	Description	Example
order	Order	Sets the order of the marks	Connected Scatterplot (Lines with Custom Paths)

Facet Channels:

Channel	Altair Class	Description	Example
column	Column	The column of a faceted plot	Trellis Scatter Plot
row	Row	The row of a faceted plot	Becker’s Barley Trellis Plot
facet	Facet	The row and/or column of a general faceted plot	US Population: Wrapped Facet

Encoding Data Types

The details of any mapping depend on the type of the data. Altair recognizes five main data types:

Data Type	Shorthand Code	Description
quantitative	Q	a continuous real-valued quantity
ordinal	O	a discrete ordered quantity
nominal	N	a discrete unordered category
temporal	T	a time or date value
geojson	G	a geographic shape

If types are not specified for data input as a DataFrame, Altair defaults to quantitative for any numeric data, temporal for date/time data, and nominal for string data, but be aware that these defaults are by no means always the correct choice!

The types can either be expressed in a long-form using the channel encoding classes such as X and Y, or in short-form using the Shorthand Syntax discussed below. For example, the following two methods of specifying the type will lead to identical plots:

alt.Chart(cars).mark_point().encode(
    x='Acceleration:Q',
    y='Miles_per_Gallon:Q',
    color='Origin:N'
)

alt.Chart(cars).mark_point().encode(
    alt.X('Acceleration', type='quantitative'),
    alt.Y('Miles_per_Gallon', type='quantitative'),
    alt.Color('Origin', type='nominal')
)

The shorthand form, x="name:Q", is useful for its lack of boilerplate when doing quick data explorations. The long-form, alt.X('name', type='quantitative'), is useful when doing more fine-tuned adjustments to the encoding, such as binning, axis and scale properties, or more.

Specifying the correct type for your data is important, as it affects the way Altair represents your encoding in the resulting plot.

Effect of Data Type on Color Scales

As an example of this, here we will represent the same data three different ways, with the color encoded as a quantitative, ordinal, and nominal type, using three vertically-concatenated charts (see Vertical Concatenation):

base = alt.Chart(cars).mark_point().encode(
    x='Horsepower:Q',
    y='Miles_per_Gallon:Q',
).properties(
    width=150,
    height=150
)

alt.vconcat(
   base.encode(color='Cylinders:Q').properties(title='quantitative'),
   base.encode(color='Cylinders:O').properties(title='ordinal'),
   base.encode(color='Cylinders:N').properties(title='nominal'),
)

The type specification influences the way Altair, via Vega-Lite, decides on the color scale to represent the value, and influences whether a discrete or continuous legend is used.

Effect of Data Type on Axis Scales

Similarly, for x and y axis encodings, the type used for the data will affect the scales used and the characteristics of the mark. For example, here is the difference between a quantitative and ordinal scale for an column that contains integers specifying a year:

pop = data.population.url

base = alt.Chart(pop).mark_bar().encode(
    alt.Y('mean(people):Q', title='total population')
).properties(
    width=200,
    height=200
)

alt.hconcat(
    base.encode(x='year:Q').properties(title='year=quantitative'),
    base.encode(x='year:O').properties(title='year=ordinal')
)

Because quantitative values do not have an inherent width, the bars do not fill the entire space between the values. This view also makes clear the missing year of data that was not immediately apparent when we treated the years as categories.

This kind of behavior is sometimes surprising to new users, but it emphasizes the importance of thinking carefully about your data types when visualizing data: a visual encoding that is suitable for categorical data may not be suitable for quantitative data, and vice versa.

Encoding Channel Options

Each encoding channel allows for a number of additional options to be expressed; these can control things like axis properties, scale properties, headers and titles, binning parameters, aggregation, sorting, and many more.

The particular options that are available vary by encoding type; the various options are listed below.

The X and Y encodings accept the following options:

Property	Type	Description
aggregate	Aggregate	Aggregation function for the field (e.g., "mean", "sum", "median", "min", "max", "count"). Default value: undefined (None) See also: aggregate documentation.
axis	anyOf(Axis, null)	An object defining properties of axis’s gridlines, ticks and labels. If null, the axis for the encoding channel will be removed. Default value: If undefined, default axis properties are applied. See also: axis documentation.
band	number	For rect-based marks (rect, bar, and image), mark size relative to bandwidth of band scales, bins or time units. If set to 1, the mark size is set to the bandwidth, the bin interval, or the time unit interval. If set to 0.5, the mark size is half of the bandwidth or the time unit interval. For other marks, relative position on a band of a stacked, binned, time unit or band scale. If set to 0, the marks will be positioned at the beginning of the band. If set to 0.5, the marks will be positioned in the middle of the band.
bin	anyOf(boolean, BinParams, string, null)	A flag for binning a quantitative field, an object defining binning parameters, or indicating that the data for x or y channel are binned before they are imported into Vega-Lite ("binned"). If true, default binning parameters will be applied. If "binned", this indicates that the data for the x (or y) channel are already binned. You can map the bin-start field to x (or y) and the bin-end field to x2 (or y2). The scale and axis will be formatted similar to binning in Vega-Lite. To adjust the axis ticks based on the bin step, you can also set the axis’s tickMinStep property. Default value: false See also: bin documentation.
field	Field	Required. A string defining the name of the field from which to pull a data value or an object defining iterated values from the repeat operator. See also: field documentation. Notes: 1) Dots (.) and brackets ([ and ]) can be used to access nested objects (e.g., "field": "foo.bar" and "field": "foo['bar']"). If field names contain dots or brackets but are not nested, you can use \\ to escape dots and brackets (e.g., "a\\.b" and "a\\[0\\]"). See more details about escaping in the field documentation. 2) field is not required if aggregate is count.
impute	anyOf(ImputeParams, null)	An object defining the properties of the Impute Operation to be applied. The field value of the other positional channel is taken as key of the Impute Operation. The field of the color channel if specified is used as groupby of the Impute Operation. See also: impute documentation.
scale	anyOf(Scale, null)	An object defining properties of the channel’s scale, which is the function that transforms values in the data domain (numbers, dates, strings, etc) to visual values (pixels, colors, sizes) of the encoding channels. If null, the scale will be disabled and the data value will be directly encoded. Default value: If undefined, default scale properties are applied. See also: scale documentation.
sort	Sort	Sort order for the encoded field. For continuous fields (quantitative or temporal), sort can be either "ascending" or "descending". For discrete fields, sort can be one of the following: - "ascending" or "descending" – for sorting by the values’ natural order in JavaScript. - A string indicating an encoding channel name to sort by (e.g., "x" or "y") with an optional minus prefix for descending sort (e.g., "-x" to sort by x-field, descending). This channel string is short-form of a sort-by-encoding definition. For example, "sort": "-x" is equivalent to "sort": {"encoding": "x", "order": "descending"}. - A sort field definition for sorting by another field. - An array specifying the field values in preferred order. In this case, the sort order will obey the values in the array, followed by any unspecified values in their original order. For discrete time field, values in the sort array can be date-time definition objects. In addition, for time units "month" and "day", the values can be the month or day names (case insensitive) or their 3-letter initials (e.g., "Mon", "Tue"). - null indicating no sort. Default value: "ascending" Note: null and sorting by another channel is not supported for row and column. See also: sort documentation.
stack	anyOf(StackOffset, null, boolean)	Type of stacking offset if the field should be stacked. stack is only applicable for x, y, theta, and radius channels with continuous domains. For example, stack of y can be used to customize stacking for a vertical bar chart. stack can be one of the following values: - "zero" or true: stacking with baseline offset at zero value of the scale (for creating typical stacked bar and area chart). - "normalize" - stacking with normalized domain (for creating normalized stacked bar and area charts. -"center" - stacking with center baseline (for streamgraph). - null or false - No-stacking. This will produce layered bar and area chart. Default value: zero for plots with all of the following conditions are true: (1) the mark is bar, area, or arc; (2) the stacked measure channel (x or y) has a linear scale; (3) At least one of non-position channels mapped to an unaggregated field that is different from x and y. Otherwise, null by default. See also: stack documentation.
timeUnit	anyOf(TimeUnit, TimeUnitParams)	Time unit (e.g., year, yearmonth, month, hours) for a temporal field. or a temporal field that gets casted as ordinal. Default value: undefined (None) See also: timeUnit documentation.
title	anyOf(Text, null)	A title for the field. If null, the title will be removed. Default value: derived from the field’s name and transformation function (aggregate, bin and timeUnit). If the field has an aggregate function, the function is displayed as part of the title (e.g., "Sum of Profit"). If the field is binned or has a time unit applied, the applied function is shown in parentheses (e.g., "Profit (binned)", "Transaction Date (year-month)"). Otherwise, the title is simply the field name. Notes: You can customize the default field title format by providing the fieldTitle property in the config or fieldTitle function via the compile function’s options. If both field definition’s title and axis, header, or legend title are defined, axis/header/legend title will be used.
type	StandardType	The type of measurement ("quantitative", "temporal", "ordinal", or "nominal") for the encoded field or constant value (datum). It can also be a "geojson" type for encoding ‘geoshape’. Vega-Lite automatically infers data types in many cases as discussed below. However, type is required for a field if: (1) the field is not nominal and the field encoding has no specified aggregate (except argmin and argmax), bin, scale type, custom sort order, nor timeUnit or (2) if you wish to use an ordinal scale for a field with bin or timeUnit. Default value: For a data field, "nominal" is the default data type unless the field encoding has aggregate, channel, bin, scale type, sort, or timeUnit that satisfies the following criteria: - "quantitative" is the default type if (1) the encoded field contains bin or aggregate except "argmin" and "argmax", (2) the encoding channel is latitude or longitude channel or (3) if the specified scale type is a quantitative scale. - "temporal" is the default type if (1) the encoded field contains timeUnit or (2) the specified scale type is a time or utc scale - ordinal"" is the default type if (1) the encoded field contains a custom sort order, (2) the specified scale type is an ordinal/point/band scale, or (3) the encoding channel is order. For a constant value in data domain (datum): - "quantitative" if the datum is a number - "nominal" if the datum is a string - "temporal" if the datum is a date time object Note: - Data type describes the semantics of the data rather than the primitive data types (number, string, etc.). The same primitive data type can have different types of measurement. For example, numeric data can represent quantitative, ordinal, or nominal data. - Data values for a temporal field can be either a date-time string (e.g., "2015-03-07 12:32:17", "17:01", "2015-03-16". "2015") or a timestamp number (e.g., 1552199579097). - When using with bin, the type property can be either "quantitative" (for using a linear bin scale) or "ordinal" (for using an ordinal bin scale). - When using with timeUnit, the type property can be either "temporal" (default, for using a temporal scale) or "ordinal" (for using an ordinal scale). - When using with aggregate, the type property refers to the post-aggregation data type. For example, we can calculate count distinct of a categorical field "cat" using {"aggregate": "distinct", "field": "cat"}. The "type" of the aggregate output is "quantitative". - Secondary channels (e.g., x2, y2, xError, yError) do not have type as they must have exactly the same type as their primary channels (e.g., x, y). See also: type documentation.

The Color, Fill, and Stroke encodings accept the following options:

Property	Type	Description
aggregate	Aggregate	Aggregation function for the field (e.g., "mean", "sum", "median", "min", "max", "count"). Default value: undefined (None) See also: aggregate documentation.
band	number	For rect-based marks (rect, bar, and image), mark size relative to bandwidth of band scales, bins or time units. If set to 1, the mark size is set to the bandwidth, the bin interval, or the time unit interval. If set to 0.5, the mark size is half of the bandwidth or the time unit interval. For other marks, relative position on a band of a stacked, binned, time unit or band scale. If set to 0, the marks will be positioned at the beginning of the band. If set to 0.5, the marks will be positioned in the middle of the band.
bin	anyOf(boolean, BinParams, null)	A flag for binning a quantitative field, an object defining binning parameters, or indicating that the data for x or y channel are binned before they are imported into Vega-Lite ("binned"). If true, default binning parameters will be applied. If "binned", this indicates that the data for the x (or y) channel are already binned. You can map the bin-start field to x (or y) and the bin-end field to x2 (or y2). The scale and axis will be formatted similar to binning in Vega-Lite. To adjust the axis ticks based on the bin step, you can also set the axis’s tickMinStep property. Default value: false See also: bin documentation.
condition	anyOf(ConditionalValueDef<(Gradient|string|null|ExprRef)>, array(ConditionalValueDef<(Gradient|string|null|ExprRef)>))	One or more value definition(s) with a selection or a test predicate. Note: A field definition’s condition property can only contain conditional value definitions since Vega-Lite only allows at most one encoded field per encoding channel.
field	Field	Required. A string defining the name of the field from which to pull a data value or an object defining iterated values from the repeat operator. See also: field documentation. Notes: 1) Dots (.) and brackets ([ and ]) can be used to access nested objects (e.g., "field": "foo.bar" and "field": "foo['bar']"). If field names contain dots or brackets but are not nested, you can use \\ to escape dots and brackets (e.g., "a\\.b" and "a\\[0\\]"). See more details about escaping in the field documentation. 2) field is not required if aggregate is count.
legend	anyOf(Legend, null)	An object defining properties of the legend. If null, the legend for the encoding channel will be removed. Default value: If undefined, default legend properties are applied. See also: legend documentation.
scale	anyOf(Scale, null)	An object defining properties of the channel’s scale, which is the function that transforms values in the data domain (numbers, dates, strings, etc) to visual values (pixels, colors, sizes) of the encoding channels. If null, the scale will be disabled and the data value will be directly encoded. Default value: If undefined, default scale properties are applied. See also: scale documentation.
sort	Sort	Sort order for the encoded field. For continuous fields (quantitative or temporal), sort can be either "ascending" or "descending". For discrete fields, sort can be one of the following: - "ascending" or "descending" – for sorting by the values’ natural order in JavaScript. - A string indicating an encoding channel name to sort by (e.g., "x" or "y") with an optional minus prefix for descending sort (e.g., "-x" to sort by x-field, descending). This channel string is short-form of a sort-by-encoding definition. For example, "sort": "-x" is equivalent to "sort": {"encoding": "x", "order": "descending"}. - A sort field definition for sorting by another field. - An array specifying the field values in preferred order. In this case, the sort order will obey the values in the array, followed by any unspecified values in their original order. For discrete time field, values in the sort array can be date-time definition objects. In addition, for time units "month" and "day", the values can be the month or day names (case insensitive) or their 3-letter initials (e.g., "Mon", "Tue"). - null indicating no sort. Default value: "ascending" Note: null and sorting by another channel is not supported for row and column. See also: sort documentation.
timeUnit	anyOf(TimeUnit, TimeUnitParams)	Time unit (e.g., year, yearmonth, month, hours) for a temporal field. or a temporal field that gets casted as ordinal. Default value: undefined (None) See also: timeUnit documentation.
title	anyOf(Text, null)	A title for the field. If null, the title will be removed. Default value: derived from the field’s name and transformation function (aggregate, bin and timeUnit). If the field has an aggregate function, the function is displayed as part of the title (e.g., "Sum of Profit"). If the field is binned or has a time unit applied, the applied function is shown in parentheses (e.g., "Profit (binned)", "Transaction Date (year-month)"). Otherwise, the title is simply the field name. Notes: You can customize the default field title format by providing the fieldTitle property in the config or fieldTitle function via the compile function’s options. If both field definition’s title and axis, header, or legend title are defined, axis/header/legend title will be used.
type	StandardType	The type of measurement ("quantitative", "temporal", "ordinal", or "nominal") for the encoded field or constant value (datum). It can also be a "geojson" type for encoding ‘geoshape’. Vega-Lite automatically infers data types in many cases as discussed below. However, type is required for a field if: (1) the field is not nominal and the field encoding has no specified aggregate (except argmin and argmax), bin, scale type, custom sort order, nor timeUnit or (2) if you wish to use an ordinal scale for a field with bin or timeUnit. Default value: For a data field, "nominal" is the default data type unless the field encoding has aggregate, channel, bin, scale type, sort, or timeUnit that satisfies the following criteria: - "quantitative" is the default type if (1) the encoded field contains bin or aggregate except "argmin" and "argmax", (2) the encoding channel is latitude or longitude channel or (3) if the specified scale type is a quantitative scale. - "temporal" is the default type if (1) the encoded field contains timeUnit or (2) the specified scale type is a time or utc scale - ordinal"" is the default type if (1) the encoded field contains a custom sort order, (2) the specified scale type is an ordinal/point/band scale, or (3) the encoding channel is order. For a constant value in data domain (datum): - "quantitative" if the datum is a number - "nominal" if the datum is a string - "temporal" if the datum is a date time object Note: - Data type describes the semantics of the data rather than the primitive data types (number, string, etc.). The same primitive data type can have different types of measurement. For example, numeric data can represent quantitative, ordinal, or nominal data. - Data values for a temporal field can be either a date-time string (e.g., "2015-03-07 12:32:17", "17:01", "2015-03-16". "2015") or a timestamp number (e.g., 1552199579097). - When using with bin, the type property can be either "quantitative" (for using a linear bin scale) or "ordinal" (for using an ordinal bin scale). - When using with timeUnit, the type property can be either "temporal" (default, for using a temporal scale) or "ordinal" (for using an ordinal scale). - When using with aggregate, the type property refers to the post-aggregation data type. For example, we can calculate count distinct of a categorical field "cat" using {"aggregate": "distinct", "field": "cat"}. The "type" of the aggregate output is "quantitative". - Secondary channels (e.g., x2, y2, xError, yError) do not have type as they must have exactly the same type as their primary channels (e.g., x, y). See also: type documentation.

The Shape encoding accepts the following options:

Property	Type	Description
aggregate	Aggregate	Aggregation function for the field (e.g., "mean", "sum", "median", "min", "max", "count"). Default value: undefined (None) See also: aggregate documentation.
band	number	For rect-based marks (rect, bar, and image), mark size relative to bandwidth of band scales, bins or time units. If set to 1, the mark size is set to the bandwidth, the bin interval, or the time unit interval. If set to 0.5, the mark size is half of the bandwidth or the time unit interval. For other marks, relative position on a band of a stacked, binned, time unit or band scale. If set to 0, the marks will be positioned at the beginning of the band. If set to 0.5, the marks will be positioned in the middle of the band.
bin	anyOf(boolean, BinParams, null)	A flag for binning a quantitative field, an object defining binning parameters, or indicating that the data for x or y channel are binned before they are imported into Vega-Lite ("binned"). If true, default binning parameters will be applied. If "binned", this indicates that the data for the x (or y) channel are already binned. You can map the bin-start field to x (or y) and the bin-end field to x2 (or y2). The scale and axis will be formatted similar to binning in Vega-Lite. To adjust the axis ticks based on the bin step, you can also set the axis’s tickMinStep property. Default value: false See also: bin documentation.
condition	anyOf(ConditionalValueDef<(string|null|ExprRef)>, array(ConditionalValueDef<(string|null|ExprRef)>))	One or more value definition(s) with a selection or a test predicate. Note: A field definition’s condition property can only contain conditional value definitions since Vega-Lite only allows at most one encoded field per encoding channel.
field	Field	Required. A string defining the name of the field from which to pull a data value or an object defining iterated values from the repeat operator. See also: field documentation. Notes: 1) Dots (.) and brackets ([ and ]) can be used to access nested objects (e.g., "field": "foo.bar" and "field": "foo['bar']"). If field names contain dots or brackets but are not nested, you can use \\ to escape dots and brackets (e.g., "a\\.b" and "a\\[0\\]"). See more details about escaping in the field documentation. 2) field is not required if aggregate is count.
legend	anyOf(Legend, null)	An object defining properties of the legend. If null, the legend for the encoding channel will be removed. Default value: If undefined, default legend properties are applied. See also: legend documentation.
scale	anyOf(Scale, null)	An object defining properties of the channel’s scale, which is the function that transforms values in the data domain (numbers, dates, strings, etc) to visual values (pixels, colors, sizes) of the encoding channels. If null, the scale will be disabled and the data value will be directly encoded. Default value: If undefined, default scale properties are applied. See also: scale documentation.
sort	Sort	Sort order for the encoded field. For continuous fields (quantitative or temporal), sort can be either "ascending" or "descending". For discrete fields, sort can be one of the following: - "ascending" or "descending" – for sorting by the values’ natural order in JavaScript. - A string indicating an encoding channel name to sort by (e.g., "x" or "y") with an optional minus prefix for descending sort (e.g., "-x" to sort by x-field, descending). This channel string is short-form of a sort-by-encoding definition. For example, "sort": "-x" is equivalent to "sort": {"encoding": "x", "order": "descending"}. - A sort field definition for sorting by another field. - An array specifying the field values in preferred order. In this case, the sort order will obey the values in the array, followed by any unspecified values in their original order. For discrete time field, values in the sort array can be date-time definition objects. In addition, for time units "month" and "day", the values can be the month or day names (case insensitive) or their 3-letter initials (e.g., "Mon", "Tue"). - null indicating no sort. Default value: "ascending" Note: null and sorting by another channel is not supported for row and column. See also: sort documentation.
timeUnit	anyOf(TimeUnit, TimeUnitParams)	Time unit (e.g., year, yearmonth, month, hours) for a temporal field. or a temporal field that gets casted as ordinal. Default value: undefined (None) See also: timeUnit documentation.
title	anyOf(Text, null)	A title for the field. If null, the title will be removed. Default value: derived from the field’s name and transformation function (aggregate, bin and timeUnit). If the field has an aggregate function, the function is displayed as part of the title (e.g., "Sum of Profit"). If the field is binned or has a time unit applied, the applied function is shown in parentheses (e.g., "Profit (binned)", "Transaction Date (year-month)"). Otherwise, the title is simply the field name. Notes: You can customize the default field title format by providing the fieldTitle property in the config or fieldTitle function via the compile function’s options. If both field definition’s title and axis, header, or legend title are defined, axis/header/legend title will be used.
type	TypeForShape	The type of measurement ("quantitative", "temporal", "ordinal", or "nominal") for the encoded field or constant value (datum). It can also be a "geojson" type for encoding ‘geoshape’. Vega-Lite automatically infers data types in many cases as discussed below. However, type is required for a field if: (1) the field is not nominal and the field encoding has no specified aggregate (except argmin and argmax), bin, scale type, custom sort order, nor timeUnit or (2) if you wish to use an ordinal scale for a field with bin or timeUnit. Default value: For a data field, "nominal" is the default data type unless the field encoding has aggregate, channel, bin, scale type, sort, or timeUnit that satisfies the following criteria: - "quantitative" is the default type if (1) the encoded field contains bin or aggregate except "argmin" and "argmax", (2) the encoding channel is latitude or longitude channel or (3) if the specified scale type is a quantitative scale. - "temporal" is the default type if (1) the encoded field contains timeUnit or (2) the specified scale type is a time or utc scale - ordinal"" is the default type if (1) the encoded field contains a custom sort order, (2) the specified scale type is an ordinal/point/band scale, or (3) the encoding channel is order. For a constant value in data domain (datum): - "quantitative" if the datum is a number - "nominal" if the datum is a string - "temporal" if the datum is a date time object Note: - Data type describes the semantics of the data rather than the primitive data types (number, string, etc.). The same primitive data type can have different types of measurement. For example, numeric data can represent quantitative, ordinal, or nominal data. - Data values for a temporal field can be either a date-time string (e.g., "2015-03-07 12:32:17", "17:01", "2015-03-16". "2015") or a timestamp number (e.g., 1552199579097). - When using with bin, the type property can be either "quantitative" (for using a linear bin scale) or "ordinal" (for using an ordinal bin scale). - When using with timeUnit, the type property can be either "temporal" (default, for using a temporal scale) or "ordinal" (for using an ordinal scale). - When using with aggregate, the type property refers to the post-aggregation data type. For example, we can calculate count distinct of a categorical field "cat" using {"aggregate": "distinct", "field": "cat"}. The "type" of the aggregate output is "quantitative". - Secondary channels (e.g., x2, y2, xError, yError) do not have type as they must have exactly the same type as their primary channels (e.g., x, y). See also: type documentation.

The Angle, FillOpacity, Opacity, Size, StrokeOpacity, and StrokeWidth encodings accept the following options:

Property	Type	Description
aggregate	Aggregate	Aggregation function for the field (e.g., "mean", "sum", "median", "min", "max", "count"). Default value: undefined (None) See also: aggregate documentation.
band	number	For rect-based marks (rect, bar, and image), mark size relative to bandwidth of band scales, bins or time units. If set to 1, the mark size is set to the bandwidth, the bin interval, or the time unit interval. If set to 0.5, the mark size is half of the bandwidth or the time unit interval. For other marks, relative position on a band of a stacked, binned, time unit or band scale. If set to 0, the marks will be positioned at the beginning of the band. If set to 0.5, the marks will be positioned in the middle of the band.
bin	anyOf(boolean, BinParams, null)	A flag for binning a quantitative field, an object defining binning parameters, or indicating that the data for x or y channel are binned before they are imported into Vega-Lite ("binned"). If true, default binning parameters will be applied. If "binned", this indicates that the data for the x (or y) channel are already binned. You can map the bin-start field to x (or y) and the bin-end field to x2 (or y2). The scale and axis will be formatted similar to binning in Vega-Lite. To adjust the axis ticks based on the bin step, you can also set the axis’s tickMinStep property. Default value: false See also: bin documentation.
condition	anyOf(ConditionalValueDef<(number|ExprRef)>, array(ConditionalValueDef<(number|ExprRef)>))	One or more value definition(s) with a selection or a test predicate. Note: A field definition’s condition property can only contain conditional value definitions since Vega-Lite only allows at most one encoded field per encoding channel.
field	Field	Required. A string defining the name of the field from which to pull a data value or an object defining iterated values from the repeat operator. See also: field documentation. Notes: 1) Dots (.) and brackets ([ and ]) can be used to access nested objects (e.g., "field": "foo.bar" and "field": "foo['bar']"). If field names contain dots or brackets but are not nested, you can use \\ to escape dots and brackets (e.g., "a\\.b" and "a\\[0\\]"). See more details about escaping in the field documentation. 2) field is not required if aggregate is count.
legend	anyOf(Legend, null)	An object defining properties of the legend. If null, the legend for the encoding channel will be removed. Default value: If undefined, default legend properties are applied. See also: legend documentation.
scale	anyOf(Scale, null)	An object defining properties of the channel’s scale, which is the function that transforms values in the data domain (numbers, dates, strings, etc) to visual values (pixels, colors, sizes) of the encoding channels. If null, the scale will be disabled and the data value will be directly encoded. Default value: If undefined, default scale properties are applied. See also: scale documentation.
sort	Sort	Sort order for the encoded field. For continuous fields (quantitative or temporal), sort can be either "ascending" or "descending". For discrete fields, sort can be one of the following: - "ascending" or "descending" – for sorting by the values’ natural order in JavaScript. - A string indicating an encoding channel name to sort by (e.g., "x" or "y") with an optional minus prefix for descending sort (e.g., "-x" to sort by x-field, descending). This channel string is short-form of a sort-by-encoding definition. For example, "sort": "-x" is equivalent to "sort": {"encoding": "x", "order": "descending"}. - A sort field definition for sorting by another field. - An array specifying the field values in preferred order. In this case, the sort order will obey the values in the array, followed by any unspecified values in their original order. For discrete time field, values in the sort array can be date-time definition objects. In addition, for time units "month" and "day", the values can be the month or day names (case insensitive) or their 3-letter initials (e.g., "Mon", "Tue"). - null indicating no sort. Default value: "ascending" Note: null and sorting by another channel is not supported for row and column. See also: sort documentation.
timeUnit	anyOf(TimeUnit, TimeUnitParams)	Time unit (e.g., year, yearmonth, month, hours) for a temporal field. or a temporal field that gets casted as ordinal. Default value: undefined (None) See also: timeUnit documentation.
title	anyOf(Text, null)	A title for the field. If null, the title will be removed. Default value: derived from the field’s name and transformation function (aggregate, bin and timeUnit). If the field has an aggregate function, the function is displayed as part of the title (e.g., "Sum of Profit"). If the field is binned or has a time unit applied, the applied function is shown in parentheses (e.g., "Profit (binned)", "Transaction Date (year-month)"). Otherwise, the title is simply the field name. Notes: You can customize the default field title format by providing the fieldTitle property in the config or fieldTitle function via the compile function’s options. If both field definition’s title and axis, header, or legend title are defined, axis/header/legend title will be used.
type	StandardType	The type of measurement ("quantitative", "temporal", "ordinal", or "nominal") for the encoded field or constant value (datum). It can also be a "geojson" type for encoding ‘geoshape’. Vega-Lite automatically infers data types in many cases as discussed below. However, type is required for a field if: (1) the field is not nominal and the field encoding has no specified aggregate (except argmin and argmax), bin, scale type, custom sort order, nor timeUnit or (2) if you wish to use an ordinal scale for a field with bin or timeUnit. Default value: For a data field, "nominal" is the default data type unless the field encoding has aggregate, channel, bin, scale type, sort, or timeUnit that satisfies the following criteria: - "quantitative" is the default type if (1) the encoded field contains bin or aggregate except "argmin" and "argmax", (2) the encoding channel is latitude or longitude channel or (3) if the specified scale type is a quantitative scale. - "temporal" is the default type if (1) the encoded field contains timeUnit or (2) the specified scale type is a time or utc scale - ordinal"" is the default type if (1) the encoded field contains a custom sort order, (2) the specified scale type is an ordinal/point/band scale, or (3) the encoding channel is order. For a constant value in data domain (datum): - "quantitative" if the datum is a number - "nominal" if the datum is a string - "temporal" if the datum is a date time object Note: - Data type describes the semantics of the data rather than the primitive data types (number, string, etc.). The same primitive data type can have different types of measurement. For example, numeric data can represent quantitative, ordinal, or nominal data. - Data values for a temporal field can be either a date-time string (e.g., "2015-03-07 12:32:17", "17:01", "2015-03-16". "2015") or a timestamp number (e.g., 1552199579097). - When using with bin, the type property can be either "quantitative" (for using a linear bin scale) or "ordinal" (for using an ordinal bin scale). - When using with timeUnit, the type property can be either "temporal" (default, for using a temporal scale) or "ordinal" (for using an ordinal scale). - When using with aggregate, the type property refers to the post-aggregation data type. For example, we can calculate count distinct of a categorical field "cat" using {"aggregate": "distinct", "field": "cat"}. The "type" of the aggregate output is "quantitative". - Secondary channels (e.g., x2, y2, xError, yError) do not have type as they must have exactly the same type as their primary channels (e.g., x, y). See also: type documentation.

The Row and Column, and Facet encodings accept the following options:

Property	Type	Description
aggregate	Aggregate	Aggregation function for the field (e.g., "mean", "sum", "median", "min", "max", "count"). Default value: undefined (None) See also: aggregate documentation.
align	LayoutAlign	The alignment to apply to row/column facet’s subplot. The supported string values are "all", "each", and "none". For "none", a flow layout will be used, in which adjacent subviews are simply placed one after the other. - For "each", subviews will be aligned into a clean grid structure, but each row or column may be of variable size. - For "all", subviews will be aligned and each row or column will be sized identically based on the maximum observed size. String values for this property will be applied to both grid rows and columns. Default value: "all".
band	number	For rect-based marks (rect, bar, and image), mark size relative to bandwidth of band scales, bins or time units. If set to 1, the mark size is set to the bandwidth, the bin interval, or the time unit interval. If set to 0.5, the mark size is half of the bandwidth or the time unit interval. For other marks, relative position on a band of a stacked, binned, time unit or band scale. If set to 0, the marks will be positioned at the beginning of the band. If set to 0.5, the marks will be positioned in the middle of the band.
bin	anyOf(boolean, BinParams, null)	A flag for binning a quantitative field, an object defining binning parameters, or indicating that the data for x or y channel are binned before they are imported into Vega-Lite ("binned"). If true, default binning parameters will be applied. If "binned", this indicates that the data for the x (or y) channel are already binned. You can map the bin-start field to x (or y) and the bin-end field to x2 (or y2). The scale and axis will be formatted similar to binning in Vega-Lite. To adjust the axis ticks based on the bin step, you can also set the axis’s tickMinStep property. Default value: false See also: bin documentation.
center	boolean	Boolean flag indicating if facet’s subviews should be centered relative to their respective rows or columns. Default value: false
field	Field	Required. A string defining the name of the field from which to pull a data value or an object defining iterated values from the repeat operator. See also: field documentation. Notes: 1) Dots (.) and brackets ([ and ]) can be used to access nested objects (e.g., "field": "foo.bar" and "field": "foo['bar']"). If field names contain dots or brackets but are not nested, you can use \\ to escape dots and brackets (e.g., "a\\.b" and "a\\[0\\]"). See more details about escaping in the field documentation. 2) field is not required if aggregate is count.
header	Header	An object defining properties of a facet’s header.
sort	anyOf(SortArray, SortOrder, EncodingSortField, null)	Sort order for the encoded field. For continuous fields (quantitative or temporal), sort can be either "ascending" or "descending". For discrete fields, sort can be one of the following: - "ascending" or "descending" – for sorting by the values’ natural order in JavaScript. - A sort field definition for sorting by another field. - An array specifying the field values in preferred order. In this case, the sort order will obey the values in the array, followed by any unspecified values in their original order. For discrete time field, values in the sort array can be date-time definition objects. In addition, for time units "month" and "day", the values can be the month or day names (case insensitive) or their 3-letter initials (e.g., "Mon", "Tue"). - null indicating no sort. Default value: "ascending" Note: null is not supported for row and column.
spacing	number	The spacing in pixels between facet’s sub-views. Default value: Depends on "spacing" property of the view composition configuration (20 by default)
timeUnit	anyOf(TimeUnit, TimeUnitParams)	Time unit (e.g., year, yearmonth, month, hours) for a temporal field. or a temporal field that gets casted as ordinal. Default value: undefined (None) See also: timeUnit documentation.
title	anyOf(Text, null)	A title for the field. If null, the title will be removed. Default value: derived from the field’s name and transformation function (aggregate, bin and timeUnit). If the field has an aggregate function, the function is displayed as part of the title (e.g., "Sum of Profit"). If the field is binned or has a time unit applied, the applied function is shown in parentheses (e.g., "Profit (binned)", "Transaction Date (year-month)"). Otherwise, the title is simply the field name. Notes: You can customize the default field title format by providing the fieldTitle property in the config or fieldTitle function via the compile function’s options. If both field definition’s title and axis, header, or legend title are defined, axis/header/legend title will be used.
type	StandardType	The type of measurement ("quantitative", "temporal", "ordinal", or "nominal") for the encoded field or constant value (datum). It can also be a "geojson" type for encoding ‘geoshape’. Vega-Lite automatically infers data types in many cases as discussed below. However, type is required for a field if: (1) the field is not nominal and the field encoding has no specified aggregate (except argmin and argmax), bin, scale type, custom sort order, nor timeUnit or (2) if you wish to use an ordinal scale for a field with bin or timeUnit. Default value: For a data field, "nominal" is the default data type unless the field encoding has aggregate, channel, bin, scale type, sort, or timeUnit that satisfies the following criteria: - "quantitative" is the default type if (1) the encoded field contains bin or aggregate except "argmin" and "argmax", (2) the encoding channel is latitude or longitude channel or (3) if the specified scale type is a quantitative scale. - "temporal" is the default type if (1) the encoded field contains timeUnit or (2) the specified scale type is a time or utc scale - ordinal"" is the default type if (1) the encoded field contains a custom sort order, (2) the specified scale type is an ordinal/point/band scale, or (3) the encoding channel is order. For a constant value in data domain (datum): - "quantitative" if the datum is a number - "nominal" if the datum is a string - "temporal" if the datum is a date time object Note: - Data type describes the semantics of the data rather than the primitive data types (number, string, etc.). The same primitive data type can have different types of measurement. For example, numeric data can represent quantitative, ordinal, or nominal data. - Data values for a temporal field can be either a date-time string (e.g., "2015-03-07 12:32:17", "17:01", "2015-03-16". "2015") or a timestamp number (e.g., 1552199579097). - When using with bin, the type property can be either "quantitative" (for using a linear bin scale) or "ordinal" (for using an ordinal bin scale). - When using with timeUnit, the type property can be either "temporal" (default, for using a temporal scale) or "ordinal" (for using an ordinal scale). - When using with aggregate, the type property refers to the post-aggregation data type. For example, we can calculate count distinct of a categorical field "cat" using {"aggregate": "distinct", "field": "cat"}. The "type" of the aggregate output is "quantitative". - Secondary channels (e.g., x2, y2, xError, yError) do not have type as they must have exactly the same type as their primary channels (e.g., x, y). See also: type documentation.

The Facet encoding accepts the following options:

Property	Type	Description
aggregate	Aggregate	Aggregation function for the field (e.g., "mean", "sum", "median", "min", "max", "count"). Default value: undefined (None) See also: aggregate documentation.
align	anyOf(LayoutAlign, RowCol<LayoutAlign>)	The alignment to apply to grid rows and columns. The supported string values are "all", "each", and "none". For "none", a flow layout will be used, in which adjacent subviews are simply placed one after the other. - For "each", subviews will be aligned into a clean grid structure, but each row or column may be of variable size. - For "all", subviews will be aligned and each row or column will be sized identically based on the maximum observed size. String values for this property will be applied to both grid rows and columns. Alternatively, an object value of the form {"row": string, "column": string} can be used to supply different alignments for rows and columns. Default value: "all".
band	number	For rect-based marks (rect, bar, and image), mark size relative to bandwidth of band scales, bins or time units. If set to 1, the mark size is set to the bandwidth, the bin interval, or the time unit interval. If set to 0.5, the mark size is half of the bandwidth or the time unit interval. For other marks, relative position on a band of a stacked, binned, time unit or band scale. If set to 0, the marks will be positioned at the beginning of the band. If set to 0.5, the marks will be positioned in the middle of the band.
bin	anyOf(boolean, BinParams, null)	A flag for binning a quantitative field, an object defining binning parameters, or indicating that the data for x or y channel are binned before they are imported into Vega-Lite ("binned"). If true, default binning parameters will be applied. If "binned", this indicates that the data for the x (or y) channel are already binned. You can map the bin-start field to x (or y) and the bin-end field to x2 (or y2). The scale and axis will be formatted similar to binning in Vega-Lite. To adjust the axis ticks based on the bin step, you can also set the axis’s tickMinStep property. Default value: false See also: bin documentation.
bounds	[‘full’, ‘flush’]	The bounds calculation method to use for determining the extent of a sub-plot. One of full (the default) or flush. If set to full, the entire calculated bounds (including axes, title, and legend) will be used. - If set to flush, only the specified width and height values for the sub-view will be used. The flush setting can be useful when attempting to place sub-plots without axes or legends into a uniform grid structure. Default value: "full"
center	anyOf(boolean, RowCol<boolean>)	Boolean flag indicating if subviews should be centered relative to their respective rows or columns. An object value of the form {"row": boolean, "column": boolean} can be used to supply different centering values for rows and columns. Default value: false
columns	number	The number of columns to include in the view composition layout. Default value: undefined – An infinite number of columns (a single row) will be assumed. This is equivalent to hconcat (for concat) and to using the column channel (for facet and repeat). Note: This property is only for: - the general (wrappable) concat operator (not hconcat/vconcat) - the facet and repeat operator with one field/repetition definition (without row/column nesting) Setting the columns to 1 is equivalent to vconcat (for concat) and to using the row channel (for facet and repeat).
field	Field	Required. A string defining the name of the field from which to pull a data value or an object defining iterated values from the repeat operator. See also: field documentation. Notes: 1) Dots (.) and brackets ([ and ]) can be used to access nested objects (e.g., "field": "foo.bar" and "field": "foo['bar']"). If field names contain dots or brackets but are not nested, you can use \\ to escape dots and brackets (e.g., "a\\.b" and "a\\[0\\]"). See more details about escaping in the field documentation. 2) field is not required if aggregate is count.
header	Header	An object defining properties of a facet’s header.
sort	anyOf(SortArray, SortOrder, EncodingSortField, null)	Sort order for the encoded field. For continuous fields (quantitative or temporal), sort can be either "ascending" or "descending". For discrete fields, sort can be one of the following: - "ascending" or "descending" – for sorting by the values’ natural order in JavaScript. - A sort field definition for sorting by another field. - An array specifying the field values in preferred order. In this case, the sort order will obey the values in the array, followed by any unspecified values in their original order. For discrete time field, values in the sort array can be date-time definition objects. In addition, for time units "month" and "day", the values can be the month or day names (case insensitive) or their 3-letter initials (e.g., "Mon", "Tue"). - null indicating no sort. Default value: "ascending" Note: null is not supported for row and column.
spacing	anyOf(number, RowCol<number>)	The spacing in pixels between sub-views of the composition operator. An object of the form {"row": number, "column": number} can be used to set different spacing values for rows and columns. Default value: Depends on "spacing" property of the view composition configuration (20 by default)
timeUnit	anyOf(TimeUnit, TimeUnitParams)	Time unit (e.g., year, yearmonth, month, hours) for a temporal field. or a temporal field that gets casted as ordinal. Default value: undefined (None) See also: timeUnit documentation.
title	anyOf(Text, null)	A title for the field. If null, the title will be removed. Default value: derived from the field’s name and transformation function (aggregate, bin and timeUnit). If the field has an aggregate function, the function is displayed as part of the title (e.g., "Sum of Profit"). If the field is binned or has a time unit applied, the applied function is shown in parentheses (e.g., "Profit (binned)", "Transaction Date (year-month)"). Otherwise, the title is simply the field name. Notes: You can customize the default field title format by providing the fieldTitle property in the config or fieldTitle function via the compile function’s options. If both field definition’s title and axis, header, or legend title are defined, axis/header/legend title will be used.
type	StandardType	The type of measurement ("quantitative", "temporal", "ordinal", or "nominal") for the encoded field or constant value (datum). It can also be a "geojson" type for encoding ‘geoshape’. Vega-Lite automatically infers data types in many cases as discussed below. However, type is required for a field if: (1) the field is not nominal and the field encoding has no specified aggregate (except argmin and argmax), bin, scale type, custom sort order, nor timeUnit or (2) if you wish to use an ordinal scale for a field with bin or timeUnit. Default value: For a data field, "nominal" is the default data type unless the field encoding has aggregate, channel, bin, scale type, sort, or timeUnit that satisfies the following criteria: - "quantitative" is the default type if (1) the encoded field contains bin or aggregate except "argmin" and "argmax", (2) the encoding channel is latitude or longitude channel or (3) if the specified scale type is a quantitative scale. - "temporal" is the default type if (1) the encoded field contains timeUnit or (2) the specified scale type is a time or utc scale - ordinal"" is the default type if (1) the encoded field contains a custom sort order, (2) the specified scale type is an ordinal/point/band scale, or (3) the encoding channel is order. For a constant value in data domain (datum): - "quantitative" if the datum is a number - "nominal" if the datum is a string - "temporal" if the datum is a date time object Note: - Data type describes the semantics of the data rather than the primitive data types (number, string, etc.). The same primitive data type can have different types of measurement. For example, numeric data can represent quantitative, ordinal, or nominal data. - Data values for a temporal field can be either a date-time string (e.g., "2015-03-07 12:32:17", "17:01", "2015-03-16". "2015") or a timestamp number (e.g., 1552199579097). - When using with bin, the type property can be either "quantitative" (for using a linear bin scale) or "ordinal" (for using an ordinal bin scale). - When using with timeUnit, the type property can be either "temporal" (default, for using a temporal scale) or "ordinal" (for using an ordinal scale). - When using with aggregate, the type property refers to the post-aggregation data type. For example, we can calculate count distinct of a categorical field "cat" using {"aggregate": "distinct", "field": "cat"}. The "type" of the aggregate output is "quantitative". - Secondary channels (e.g., x2, y2, xError, yError) do not have type as they must have exactly the same type as their primary channels (e.g., x, y). See also: type documentation.

The Text encoding accepts the following options:

Property	Type	Description
aggregate	Aggregate	Aggregation function for the field (e.g., "mean", "sum", "median", "min", "max", "count"). Default value: undefined (None) See also: aggregate documentation.
band	number	For rect-based marks (rect, bar, and image), mark size relative to bandwidth of band scales, bins or time units. If set to 1, the mark size is set to the bandwidth, the bin interval, or the time unit interval. If set to 0.5, the mark size is half of the bandwidth or the time unit interval. For other marks, relative position on a band of a stacked, binned, time unit or band scale. If set to 0, the marks will be positioned at the beginning of the band. If set to 0.5, the marks will be positioned in the middle of the band.
bin	anyOf(boolean, BinParams, string, null)	A flag for binning a quantitative field, an object defining binning parameters, or indicating that the data for x or y channel are binned before they are imported into Vega-Lite ("binned"). If true, default binning parameters will be applied. If "binned", this indicates that the data for the x (or y) channel are already binned. You can map the bin-start field to x (or y) and the bin-end field to x2 (or y2). The scale and axis will be formatted similar to binning in Vega-Lite. To adjust the axis ticks based on the bin step, you can also set the axis’s tickMinStep property. Default value: false See also: bin documentation.
condition	anyOf(ConditionalValueDef<(Text|ExprRef)>, array(ConditionalValueDef<(Text|ExprRef)>))	One or more value definition(s) with a selection or a test predicate. Note: A field definition’s condition property can only contain conditional value definitions since Vega-Lite only allows at most one encoded field per encoding channel.
field	Field	Required. A string defining the name of the field from which to pull a data value or an object defining iterated values from the repeat operator. See also: field documentation. Notes: 1) Dots (.) and brackets ([ and ]) can be used to access nested objects (e.g., "field": "foo.bar" and "field": "foo['bar']"). If field names contain dots or brackets but are not nested, you can use \\ to escape dots and brackets (e.g., "a\\.b" and "a\\[0\\]"). See more details about escaping in the field documentation. 2) field is not required if aggregate is count.
format	anyOf(string, Dict<unknown>)	When used with the default "number" and "time" format type, the text formatting pattern for labels of guides (axes, legends, headers) and text marks. If the format type is "number" (e.g., for quantitative fields), this is D3’s number format pattern. - If the format type is "time" (e.g., for temporal fields), this is D3’s time format pattern. See the format documentation for more examples. When used with a custom formatType, this value will be passed as format alongside datum.value to the registered function. Default value: Derived from numberFormat config for number format and from timeFormat config for time format.
formatType	string	The format type for labels. One of "number", "time", or a registered custom format type. Default value: - "time" for temporal fields and ordinal and nominal fields with timeUnit. - "number" for quantitative fields as well as ordinal and nominal fields without timeUnit.
labelExpr	string	Vega expression for customizing labels text. Note: The label text and value can be assessed via the label and value properties of the axis’s backing datum object.
timeUnit	anyOf(TimeUnit, TimeUnitParams)	Time unit (e.g., year, yearmonth, month, hours) for a temporal field. or a temporal field that gets casted as ordinal. Default value: undefined (None) See also: timeUnit documentation.
title	anyOf(Text, null)	A title for the field. If null, the title will be removed. Default value: derived from the field’s name and transformation function (aggregate, bin and timeUnit). If the field has an aggregate function, the function is displayed as part of the title (e.g., "Sum of Profit"). If the field is binned or has a time unit applied, the applied function is shown in parentheses (e.g., "Profit (binned)", "Transaction Date (year-month)"). Otherwise, the title is simply the field name. Notes: You can customize the default field title format by providing the fieldTitle property in the config or fieldTitle function via the compile function’s options. If both field definition’s title and axis, header, or legend title are defined, axis/header/legend title will be used.
type	StandardType	The type of measurement ("quantitative", "temporal", "ordinal", or "nominal") for the encoded field or constant value (datum). It can also be a "geojson" type for encoding ‘geoshape’. Vega-Lite automatically infers data types in many cases as discussed below. However, type is required for a field if: (1) the field is not nominal and the field encoding has no specified aggregate (except argmin and argmax), bin, scale type, custom sort order, nor timeUnit or (2) if you wish to use an ordinal scale for a field with bin or timeUnit. Default value: For a data field, "nominal" is the default data type unless the field encoding has aggregate, channel, bin, scale type, sort, or timeUnit that satisfies the following criteria: - "quantitative" is the default type if (1) the encoded field contains bin or aggregate except "argmin" and "argmax", (2) the encoding channel is latitude or longitude channel or (3) if the specified scale type is a quantitative scale. - "temporal" is the default type if (1) the encoded field contains timeUnit or (2) the specified scale type is a time or utc scale - ordinal"" is the default type if (1) the encoded field contains a custom sort order, (2) the specified scale type is an ordinal/point/band scale, or (3) the encoding channel is order. For a constant value in data domain (datum): - "quantitative" if the datum is a number - "nominal" if the datum is a string - "temporal" if the datum is a date time object Note: - Data type describes the semantics of the data rather than the primitive data types (number, string, etc.). The same primitive data type can have different types of measurement. For example, numeric data can represent quantitative, ordinal, or nominal data. - Data values for a temporal field can be either a date-time string (e.g., "2015-03-07 12:32:17", "17:01", "2015-03-16". "2015") or a timestamp number (e.g., 1552199579097). - When using with bin, the type property can be either "quantitative" (for using a linear bin scale) or "ordinal" (for using an ordinal bin scale). - When using with timeUnit, the type property can be either "temporal" (default, for using a temporal scale) or "ordinal" (for using an ordinal scale). - When using with aggregate, the type property refers to the post-aggregation data type. For example, we can calculate count distinct of a categorical field "cat" using {"aggregate": "distinct", "field": "cat"}. The "type" of the aggregate output is "quantitative". - Secondary channels (e.g., x2, y2, xError, yError) do not have type as they must have exactly the same type as their primary channels (e.g., x, y). See also: type documentation.

The Description, Href, Tooltip, and Url encodings accept the following options:

Property	Type	Description
aggregate	Aggregate	Aggregation function for the field (e.g., "mean", "sum", "median", "min", "max", "count"). Default value: undefined (None) See also: aggregate documentation.
band	number	For rect-based marks (rect, bar, and image), mark size relative to bandwidth of band scales, bins or time units. If set to 1, the mark size is set to the bandwidth, the bin interval, or the time unit interval. If set to 0.5, the mark size is half of the bandwidth or the time unit interval. For other marks, relative position on a band of a stacked, binned, time unit or band scale. If set to 0, the marks will be positioned at the beginning of the band. If set to 0.5, the marks will be positioned in the middle of the band.
bin	anyOf(boolean, BinParams, string, null)	A flag for binning a quantitative field, an object defining binning parameters, or indicating that the data for x or y channel are binned before they are imported into Vega-Lite ("binned"). If true, default binning parameters will be applied. If "binned", this indicates that the data for the x (or y) channel are already binned. You can map the bin-start field to x (or y) and the bin-end field to x2 (or y2). The scale and axis will be formatted similar to binning in Vega-Lite. To adjust the axis ticks based on the bin step, you can also set the axis’s tickMinStep property. Default value: false See also: bin documentation.
condition	anyOf(ConditionalValueDef<(string|ExprRef)>, array(ConditionalValueDef<(string|ExprRef)>))	One or more value definition(s) with a selection or a test predicate. Note: A field definition’s condition property can only contain conditional value definitions since Vega-Lite only allows at most one encoded field per encoding channel.
field	Field	Required. A string defining the name of the field from which to pull a data value or an object defining iterated values from the repeat operator. See also: field documentation. Notes: 1) Dots (.) and brackets ([ and ]) can be used to access nested objects (e.g., "field": "foo.bar" and "field": "foo['bar']"). If field names contain dots or brackets but are not nested, you can use \\ to escape dots and brackets (e.g., "a\\.b" and "a\\[0\\]"). See more details about escaping in the field documentation. 2) field is not required if aggregate is count.
format	anyOf(string, Dict<unknown>)	When used with the default "number" and "time" format type, the text formatting pattern for labels of guides (axes, legends, headers) and text marks. If the format type is "number" (e.g., for quantitative fields), this is D3’s number format pattern. - If the format type is "time" (e.g., for temporal fields), this is D3’s time format pattern. See the format documentation for more examples. When used with a custom formatType, this value will be passed as format alongside datum.value to the registered function. Default value: Derived from numberFormat config for number format and from timeFormat config for time format.
formatType	string	The format type for labels. One of "number", "time", or a registered custom format type. Default value: - "time" for temporal fields and ordinal and nominal fields with timeUnit. - "number" for quantitative fields as well as ordinal and nominal fields without timeUnit.
labelExpr	string	Vega expression for customizing labels text. Note: The label text and value can be assessed via the label and value properties of the axis’s backing datum object.
timeUnit	anyOf(TimeUnit, TimeUnitParams)	Time unit (e.g., year, yearmonth, month, hours) for a temporal field. or a temporal field that gets casted as ordinal. Default value: undefined (None) See also: timeUnit documentation.
title	anyOf(Text, null)	A title for the field. If null, the title will be removed. Default value: derived from the field’s name and transformation function (aggregate, bin and timeUnit). If the field has an aggregate function, the function is displayed as part of the title (e.g., "Sum of Profit"). If the field is binned or has a time unit applied, the applied function is shown in parentheses (e.g., "Profit (binned)", "Transaction Date (year-month)"). Otherwise, the title is simply the field name. Notes: You can customize the default field title format by providing the fieldTitle property in the config or fieldTitle function via the compile function’s options. If both field definition’s title and axis, header, or legend title are defined, axis/header/legend title will be used.
type	StandardType	The type of measurement ("quantitative", "temporal", "ordinal", or "nominal") for the encoded field or constant value (datum). It can also be a "geojson" type for encoding ‘geoshape’. Vega-Lite automatically infers data types in many cases as discussed below. However, type is required for a field if: (1) the field is not nominal and the field encoding has no specified aggregate (except argmin and argmax), bin, scale type, custom sort order, nor timeUnit or (2) if you wish to use an ordinal scale for a field with bin or timeUnit. Default value: For a data field, "nominal" is the default data type unless the field encoding has aggregate, channel, bin, scale type, sort, or timeUnit that satisfies the following criteria: - "quantitative" is the default type if (1) the encoded field contains bin or aggregate except "argmin" and "argmax", (2) the encoding channel is latitude or longitude channel or (3) if the specified scale type is a quantitative scale. - "temporal" is the default type if (1) the encoded field contains timeUnit or (2) the specified scale type is a time or utc scale - ordinal"" is the default type if (1) the encoded field contains a custom sort order, (2) the specified scale type is an ordinal/point/band scale, or (3) the encoding channel is order. For a constant value in data domain (datum): - "quantitative" if the datum is a number - "nominal" if the datum is a string - "temporal" if the datum is a date time object Note: - Data type describes the semantics of the data rather than the primitive data types (number, string, etc.). The same primitive data type can have different types of measurement. For example, numeric data can represent quantitative, ordinal, or nominal data. - Data values for a temporal field can be either a date-time string (e.g., "2015-03-07 12:32:17", "17:01", "2015-03-16". "2015") or a timestamp number (e.g., 1552199579097). - When using with bin, the type property can be either "quantitative" (for using a linear bin scale) or "ordinal" (for using an ordinal bin scale). - When using with timeUnit, the type property can be either "temporal" (default, for using a temporal scale) or "ordinal" (for using an ordinal scale). - When using with aggregate, the type property refers to the post-aggregation data type. For example, we can calculate count distinct of a categorical field "cat" using {"aggregate": "distinct", "field": "cat"}. The "type" of the aggregate output is "quantitative". - Secondary channels (e.g., x2, y2, xError, yError) do not have type as they must have exactly the same type as their primary channels (e.g., x, y). See also: type documentation.

The Detail and Key encodings accept the following options:

Property	Type	Description
aggregate	Aggregate	Aggregation function for the field (e.g., "mean", "sum", "median", "min", "max", "count"). Default value: undefined (None) See also: aggregate documentation.
band	number	For rect-based marks (rect, bar, and image), mark size relative to bandwidth of band scales, bins or time units. If set to 1, the mark size is set to the bandwidth, the bin interval, or the time unit interval. If set to 0.5, the mark size is half of the bandwidth or the time unit interval. For other marks, relative position on a band of a stacked, binned, time unit or band scale. If set to 0, the marks will be positioned at the beginning of the band. If set to 0.5, the marks will be positioned in the middle of the band.
bin	anyOf(boolean, BinParams, string, null)	A flag for binning a quantitative field, an object defining binning parameters, or indicating that the data for x or y channel are binned before they are imported into Vega-Lite ("binned"). If true, default binning parameters will be applied. If "binned", this indicates that the data for the x (or y) channel are already binned. You can map the bin-start field to x (or y) and the bin-end field to x2 (or y2). The scale and axis will be formatted similar to binning in Vega-Lite. To adjust the axis ticks based on the bin step, you can also set the axis’s tickMinStep property. Default value: false See also: bin documentation.
field	Field	Required. A string defining the name of the field from which to pull a data value or an object defining iterated values from the repeat operator. See also: field documentation. Notes: 1) Dots (.) and brackets ([ and ]) can be used to access nested objects (e.g., "field": "foo.bar" and "field": "foo['bar']"). If field names contain dots or brackets but are not nested, you can use \\ to escape dots and brackets (e.g., "a\\.b" and "a\\[0\\]"). See more details about escaping in the field documentation. 2) field is not required if aggregate is count.
timeUnit	anyOf(TimeUnit, TimeUnitParams)	Time unit (e.g., year, yearmonth, month, hours) for a temporal field. or a temporal field that gets casted as ordinal. Default value: undefined (None) See also: timeUnit documentation.
title	anyOf(Text, null)	A title for the field. If null, the title will be removed. Default value: derived from the field’s name and transformation function (aggregate, bin and timeUnit). If the field has an aggregate function, the function is displayed as part of the title (e.g., "Sum of Profit"). If the field is binned or has a time unit applied, the applied function is shown in parentheses (e.g., "Profit (binned)", "Transaction Date (year-month)"). Otherwise, the title is simply the field name. Notes: You can customize the default field title format by providing the fieldTitle property in the config or fieldTitle function via the compile function’s options. If both field definition’s title and axis, header, or legend title are defined, axis/header/legend title will be used.
type	StandardType	The type of measurement ("quantitative", "temporal", "ordinal", or "nominal") for the encoded field or constant value (datum). It can also be a "geojson" type for encoding ‘geoshape’. Vega-Lite automatically infers data types in many cases as discussed below. However, type is required for a field if: (1) the field is not nominal and the field encoding has no specified aggregate (except argmin and argmax), bin, scale type, custom sort order, nor timeUnit or (2) if you wish to use an ordinal scale for a field with bin or timeUnit. Default value: For a data field, "nominal" is the default data type unless the field encoding has aggregate, channel, bin, scale type, sort, or timeUnit that satisfies the following criteria: - "quantitative" is the default type if (1) the encoded field contains bin or aggregate except "argmin" and "argmax", (2) the encoding channel is latitude or longitude channel or (3) if the specified scale type is a quantitative scale. - "temporal" is the default type if (1) the encoded field contains timeUnit or (2) the specified scale type is a time or utc scale - ordinal"" is the default type if (1) the encoded field contains a custom sort order, (2) the specified scale type is an ordinal/point/band scale, or (3) the encoding channel is order. For a constant value in data domain (datum): - "quantitative" if the datum is a number - "nominal" if the datum is a string - "temporal" if the datum is a date time object Note: - Data type describes the semantics of the data rather than the primitive data types (number, string, etc.). The same primitive data type can have different types of measurement. For example, numeric data can represent quantitative, ordinal, or nominal data. - Data values for a temporal field can be either a date-time string (e.g., "2015-03-07 12:32:17", "17:01", "2015-03-16". "2015") or a timestamp number (e.g., 1552199579097). - When using with bin, the type property can be either "quantitative" (for using a linear bin scale) or "ordinal" (for using an ordinal bin scale). - When using with timeUnit, the type property can be either "temporal" (default, for using a temporal scale) or "ordinal" (for using an ordinal scale). - When using with aggregate, the type property refers to the post-aggregation data type. For example, we can calculate count distinct of a categorical field "cat" using {"aggregate": "distinct", "field": "cat"}. The "type" of the aggregate output is "quantitative". - Secondary channels (e.g., x2, y2, xError, yError) do not have type as they must have exactly the same type as their primary channels (e.g., x, y). See also: type documentation.

The Latitude and Longitude encodings accept the following options:

Property	Type	Description
aggregate	Aggregate	Aggregation function for the field (e.g., "mean", "sum", "median", "min", "max", "count"). Default value: undefined (None) See also: aggregate documentation.
band	number	For rect-based marks (rect, bar, and image), mark size relative to bandwidth of band scales, bins or time units. If set to 1, the mark size is set to the bandwidth, the bin interval, or the time unit interval. If set to 0.5, the mark size is half of the bandwidth or the time unit interval. For other marks, relative position on a band of a stacked, binned, time unit or band scale. If set to 0, the marks will be positioned at the beginning of the band. If set to 0.5, the marks will be positioned in the middle of the band.
bin	null	A flag for binning a quantitative field, an object defining binning parameters, or indicating that the data for x or y channel are binned before they are imported into Vega-Lite ("binned"). If true, default binning parameters will be applied. If "binned", this indicates that the data for the x (or y) channel are already binned. You can map the bin-start field to x (or y) and the bin-end field to x2 (or y2). The scale and axis will be formatted similar to binning in Vega-Lite. To adjust the axis ticks based on the bin step, you can also set the axis’s tickMinStep property. Default value: false See also: bin documentation.
field	Field	Required. A string defining the name of the field from which to pull a data value or an object defining iterated values from the repeat operator. See also: field documentation. Notes: 1) Dots (.) and brackets ([ and ]) can be used to access nested objects (e.g., "field": "foo.bar" and "field": "foo['bar']"). If field names contain dots or brackets but are not nested, you can use \\ to escape dots and brackets (e.g., "a\\.b" and "a\\[0\\]"). See more details about escaping in the field documentation. 2) field is not required if aggregate is count.
timeUnit	anyOf(TimeUnit, TimeUnitParams)	Time unit (e.g., year, yearmonth, month, hours) for a temporal field. or a temporal field that gets casted as ordinal. Default value: undefined (None) See also: timeUnit documentation.
title	anyOf(Text, null)	A title for the field. If null, the title will be removed. Default value: derived from the field’s name and transformation function (aggregate, bin and timeUnit). If the field has an aggregate function, the function is displayed as part of the title (e.g., "Sum of Profit"). If the field is binned or has a time unit applied, the applied function is shown in parentheses (e.g., "Profit (binned)", "Transaction Date (year-month)"). Otherwise, the title is simply the field name. Notes: You can customize the default field title format by providing the fieldTitle property in the config or fieldTitle function via the compile function’s options. If both field definition’s title and axis, header, or legend title are defined, axis/header/legend title will be used.
type	string	The type of measurement ("quantitative", "temporal", "ordinal", or "nominal") for the encoded field or constant value (datum). It can also be a "geojson" type for encoding ‘geoshape’. Vega-Lite automatically infers data types in many cases as discussed below. However, type is required for a field if: (1) the field is not nominal and the field encoding has no specified aggregate (except argmin and argmax), bin, scale type, custom sort order, nor timeUnit or (2) if you wish to use an ordinal scale for a field with bin or timeUnit. Default value: For a data field, "nominal" is the default data type unless the field encoding has aggregate, channel, bin, scale type, sort, or timeUnit that satisfies the following criteria: - "quantitative" is the default type if (1) the encoded field contains bin or aggregate except "argmin" and "argmax", (2) the encoding channel is latitude or longitude channel or (3) if the specified scale type is a quantitative scale. - "temporal" is the default type if (1) the encoded field contains timeUnit or (2) the specified scale type is a time or utc scale - ordinal"" is the default type if (1) the encoded field contains a custom sort order, (2) the specified scale type is an ordinal/point/band scale, or (3) the encoding channel is order. For a constant value in data domain (datum): - "quantitative" if the datum is a number - "nominal" if the datum is a string - "temporal" if the datum is a date time object Note: - Data type describes the semantics of the data rather than the primitive data types (number, string, etc.). The same primitive data type can have different types of measurement. For example, numeric data can represent quantitative, ordinal, or nominal data. - Data values for a temporal field can be either a date-time string (e.g., "2015-03-07 12:32:17", "17:01", "2015-03-16". "2015") or a timestamp number (e.g., 1552199579097). - When using with bin, the type property can be either "quantitative" (for using a linear bin scale) or "ordinal" (for using an ordinal bin scale). - When using with timeUnit, the type property can be either "temporal" (default, for using a temporal scale) or "ordinal" (for using an ordinal scale). - When using with aggregate, the type property refers to the post-aggregation data type. For example, we can calculate count distinct of a categorical field "cat" using {"aggregate": "distinct", "field": "cat"}. The "type" of the aggregate output is "quantitative". - Secondary channels (e.g., x2, y2, xError, yError) do not have type as they must have exactly the same type as their primary channels (e.g., x, y). See also: type documentation.

The Latitude2, Longitude2, Radius2, Theta2, X2, Y2, XError, YError, XError2, and YError2 encodings accept the following options:

Property	Type	Description
aggregate	Aggregate	Aggregation function for the field (e.g., "mean", "sum", "median", "min", "max", "count"). Default value: undefined (None) See also: aggregate documentation.
band	number	For rect-based marks (rect, bar, and image), mark size relative to bandwidth of band scales, bins or time units. If set to 1, the mark size is set to the bandwidth, the bin interval, or the time unit interval. If set to 0.5, the mark size is half of the bandwidth or the time unit interval. For other marks, relative position on a band of a stacked, binned, time unit or band scale. If set to 0, the marks will be positioned at the beginning of the band. If set to 0.5, the marks will be positioned in the middle of the band.
bin	null	A flag for binning a quantitative field, an object defining binning parameters, or indicating that the data for x or y channel are binned before they are imported into Vega-Lite ("binned"). If true, default binning parameters will be applied. If "binned", this indicates that the data for the x (or y) channel are already binned. You can map the bin-start field to x (or y) and the bin-end field to x2 (or y2). The scale and axis will be formatted similar to binning in Vega-Lite. To adjust the axis ticks based on the bin step, you can also set the axis’s tickMinStep property. Default value: false See also: bin documentation.
field	Field	Required. A string defining the name of the field from which to pull a data value or an object defining iterated values from the repeat operator. See also: field documentation. Notes: 1) Dots (.) and brackets ([ and ]) can be used to access nested objects (e.g., "field": "foo.bar" and "field": "foo['bar']"). If field names contain dots or brackets but are not nested, you can use \\ to escape dots and brackets (e.g., "a\\.b" and "a\\[0\\]"). See more details about escaping in the field documentation. 2) field is not required if aggregate is count.
timeUnit	anyOf(TimeUnit, TimeUnitParams)	Time unit (e.g., year, yearmonth, month, hours) for a temporal field. or a temporal field that gets casted as ordinal. Default value: undefined (None) See also: timeUnit documentation.
title	anyOf(Text, null)	A title for the field. If null, the title will be removed. Default value: derived from the field’s name and transformation function (aggregate, bin and timeUnit). If the field has an aggregate function, the function is displayed as part of the title (e.g., "Sum of Profit"). If the field is binned or has a time unit applied, the applied function is shown in parentheses (e.g., "Profit (binned)", "Transaction Date (year-month)"). Otherwise, the title is simply the field name. Notes: You can customize the default field title format by providing the fieldTitle property in the config or fieldTitle function via the compile function’s options. If both field definition’s title and axis, header, or legend title are defined, axis/header/legend title will be used.

The Order encoding accepts the following options:

Property	Type	Description
aggregate	Aggregate	Aggregation function for the field (e.g., "mean", "sum", "median", "min", "max", "count"). Default value: undefined (None) See also: aggregate documentation.
band	number	For rect-based marks (rect, bar, and image), mark size relative to bandwidth of band scales, bins or time units. If set to 1, the mark size is set to the bandwidth, the bin interval, or the time unit interval. If set to 0.5, the mark size is half of the bandwidth or the time unit interval. For other marks, relative position on a band of a stacked, binned, time unit or band scale. If set to 0, the marks will be positioned at the beginning of the band. If set to 0.5, the marks will be positioned in the middle of the band.
bin	anyOf(boolean, BinParams, string, null)	A flag for binning a quantitative field, an object defining binning parameters, or indicating that the data for x or y channel are binned before they are imported into Vega-Lite ("binned"). If true, default binning parameters will be applied. If "binned", this indicates that the data for the x (or y) channel are already binned. You can map the bin-start field to x (or y) and the bin-end field to x2 (or y2). The scale and axis will be formatted similar to binning in Vega-Lite. To adjust the axis ticks based on the bin step, you can also set the axis’s tickMinStep property. Default value: false See also: bin documentation.
field	Field	Required. A string defining the name of the field from which to pull a data value or an object defining iterated values from the repeat operator. See also: field documentation. Notes: 1) Dots (.) and brackets ([ and ]) can be used to access nested objects (e.g., "field": "foo.bar" and "field": "foo['bar']"). If field names contain dots or brackets but are not nested, you can use \\ to escape dots and brackets (e.g., "a\\.b" and "a\\[0\\]"). See more details about escaping in the field documentation. 2) field is not required if aggregate is count.
sort	SortOrder	The sort order. One of "ascending" (default) or "descending".
timeUnit	anyOf(TimeUnit, TimeUnitParams)	Time unit (e.g., year, yearmonth, month, hours) for a temporal field. or a temporal field that gets casted as ordinal. Default value: undefined (None) See also: timeUnit documentation.
title	anyOf(Text, null)	A title for the field. If null, the title will be removed. Default value: derived from the field’s name and transformation function (aggregate, bin and timeUnit). If the field has an aggregate function, the function is displayed as part of the title (e.g., "Sum of Profit"). If the field is binned or has a time unit applied, the applied function is shown in parentheses (e.g., "Profit (binned)", "Transaction Date (year-month)"). Otherwise, the title is simply the field name. Notes: You can customize the default field title format by providing the fieldTitle property in the config or fieldTitle function via the compile function’s options. If both field definition’s title and axis, header, or legend title are defined, axis/header/legend title will be used.
type	StandardType	The type of measurement ("quantitative", "temporal", "ordinal", or "nominal") for the encoded field or constant value (datum). It can also be a "geojson" type for encoding ‘geoshape’. Vega-Lite automatically infers data types in many cases as discussed below. However, type is required for a field if: (1) the field is not nominal and the field encoding has no specified aggregate (except argmin and argmax), bin, scale type, custom sort order, nor timeUnit or (2) if you wish to use an ordinal scale for a field with bin or timeUnit. Default value: For a data field, "nominal" is the default data type unless the field encoding has aggregate, channel, bin, scale type, sort, or timeUnit that satisfies the following criteria: - "quantitative" is the default type if (1) the encoded field contains bin or aggregate except "argmin" and "argmax", (2) the encoding channel is latitude or longitude channel or (3) if the specified scale type is a quantitative scale. - "temporal" is the default type if (1) the encoded field contains timeUnit or (2) the specified scale type is a time or utc scale - ordinal"" is the default type if (1) the encoded field contains a custom sort order, (2) the specified scale type is an ordinal/point/band scale, or (3) the encoding channel is order. For a constant value in data domain (datum): - "quantitative" if the datum is a number - "nominal" if the datum is a string - "temporal" if the datum is a date time object Note: - Data type describes the semantics of the data rather than the primitive data types (number, string, etc.). The same primitive data type can have different types of measurement. For example, numeric data can represent quantitative, ordinal, or nominal data. - Data values for a temporal field can be either a date-time string (e.g., "2015-03-07 12:32:17", "17:01", "2015-03-16". "2015") or a timestamp number (e.g., 1552199579097). - When using with bin, the type property can be either "quantitative" (for using a linear bin scale) or "ordinal" (for using an ordinal bin scale). - When using with timeUnit, the type property can be either "temporal" (default, for using a temporal scale) or "ordinal" (for using an ordinal scale). - When using with aggregate, the type property refers to the post-aggregation data type. For example, we can calculate count distinct of a categorical field "cat" using {"aggregate": "distinct", "field": "cat"}. The "type" of the aggregate output is "quantitative". - Secondary channels (e.g., x2, y2, xError, yError) do not have type as they must have exactly the same type as their primary channels (e.g., x, y). See also: type documentation.

The Radius and Theta encodings accept the following options:

Property	Type	Description
aggregate	Aggregate	Aggregation function for the field (e.g., "mean", "sum", "median", "min", "max", "count"). Default value: undefined (None) See also: aggregate documentation.
band	number	For rect-based marks (rect, bar, and image), mark size relative to bandwidth of band scales, bins or time units. If set to 1, the mark size is set to the bandwidth, the bin interval, or the time unit interval. If set to 0.5, the mark size is half of the bandwidth or the time unit interval. For other marks, relative position on a band of a stacked, binned, time unit or band scale. If set to 0, the marks will be positioned at the beginning of the band. If set to 0.5, the marks will be positioned in the middle of the band.
bin	anyOf(boolean, BinParams, string, null)	A flag for binning a quantitative field, an object defining binning parameters, or indicating that the data for x or y channel are binned before they are imported into Vega-Lite ("binned"). If true, default binning parameters will be applied. If "binned", this indicates that the data for the x (or y) channel are already binned. You can map the bin-start field to x (or y) and the bin-end field to x2 (or y2). The scale and axis will be formatted similar to binning in Vega-Lite. To adjust the axis ticks based on the bin step, you can also set the axis’s tickMinStep property. Default value: false See also: bin documentation.
field	Field	Required. A string defining the name of the field from which to pull a data value or an object defining iterated values from the repeat operator. See also: field documentation. Notes: 1) Dots (.) and brackets ([ and ]) can be used to access nested objects (e.g., "field": "foo.bar" and "field": "foo['bar']"). If field names contain dots or brackets but are not nested, you can use \\ to escape dots and brackets (e.g., "a\\.b" and "a\\[0\\]"). See more details about escaping in the field documentation. 2) field is not required if aggregate is count.
scale	anyOf(Scale, null)	An object defining properties of the channel’s scale, which is the function that transforms values in the data domain (numbers, dates, strings, etc) to visual values (pixels, colors, sizes) of the encoding channels. If null, the scale will be disabled and the data value will be directly encoded. Default value: If undefined, default scale properties are applied. See also: scale documentation.
sort	Sort	Sort order for the encoded field. For continuous fields (quantitative or temporal), sort can be either "ascending" or "descending". For discrete fields, sort can be one of the following: - "ascending" or "descending" – for sorting by the values’ natural order in JavaScript. - A string indicating an encoding channel name to sort by (e.g., "x" or "y") with an optional minus prefix for descending sort (e.g., "-x" to sort by x-field, descending). This channel string is short-form of a sort-by-encoding definition. For example, "sort": "-x" is equivalent to "sort": {"encoding": "x", "order": "descending"}. - A sort field definition for sorting by another field. - An array specifying the field values in preferred order. In this case, the sort order will obey the values in the array, followed by any unspecified values in their original order. For discrete time field, values in the sort array can be date-time definition objects. In addition, for time units "month" and "day", the values can be the month or day names (case insensitive) or their 3-letter initials (e.g., "Mon", "Tue"). - null indicating no sort. Default value: "ascending" Note: null and sorting by another channel is not supported for row and column. See also: sort documentation.
stack	anyOf(StackOffset, null, boolean)	Type of stacking offset if the field should be stacked. stack is only applicable for x, y, theta, and radius channels with continuous domains. For example, stack of y can be used to customize stacking for a vertical bar chart. stack can be one of the following values: - "zero" or true: stacking with baseline offset at zero value of the scale (for creating typical stacked bar and area chart). - "normalize" - stacking with normalized domain (for creating normalized stacked bar and area charts. -"center" - stacking with center baseline (for streamgraph). - null or false - No-stacking. This will produce layered bar and area chart. Default value: zero for plots with all of the following conditions are true: (1) the mark is bar, area, or arc; (2) the stacked measure channel (x or y) has a linear scale; (3) At least one of non-position channels mapped to an unaggregated field that is different from x and y. Otherwise, null by default. See also: stack documentation.
timeUnit	anyOf(TimeUnit, TimeUnitParams)	Time unit (e.g., year, yearmonth, month, hours) for a temporal field. or a temporal field that gets casted as ordinal. Default value: undefined (None) See also: timeUnit documentation.
title	anyOf(Text, null)	A title for the field. If null, the title will be removed. Default value: derived from the field’s name and transformation function (aggregate, bin and timeUnit). If the field has an aggregate function, the function is displayed as part of the title (e.g., "Sum of Profit"). If the field is binned or has a time unit applied, the applied function is shown in parentheses (e.g., "Profit (binned)", "Transaction Date (year-month)"). Otherwise, the title is simply the field name. Notes: You can customize the default field title format by providing the fieldTitle property in the config or fieldTitle function via the compile function’s options. If both field definition’s title and axis, header, or legend title are defined, axis/header/legend title will be used.
type	StandardType	The type of measurement ("quantitative", "temporal", "ordinal", or "nominal") for the encoded field or constant value (datum). It can also be a "geojson" type for encoding ‘geoshape’. Vega-Lite automatically infers data types in many cases as discussed below. However, type is required for a field if: (1) the field is not nominal and the field encoding has no specified aggregate (except argmin and argmax), bin, scale type, custom sort order, nor timeUnit or (2) if you wish to use an ordinal scale for a field with bin or timeUnit. Default value: For a data field, "nominal" is the default data type unless the field encoding has aggregate, channel, bin, scale type, sort, or timeUnit that satisfies the following criteria: - "quantitative" is the default type if (1) the encoded field contains bin or aggregate except "argmin" and "argmax", (2) the encoding channel is latitude or longitude channel or (3) if the specified scale type is a quantitative scale. - "temporal" is the default type if (1) the encoded field contains timeUnit or (2) the specified scale type is a time or utc scale - ordinal"" is the default type if (1) the encoded field contains a custom sort order, (2) the specified scale type is an ordinal/point/band scale, or (3) the encoding channel is order. For a constant value in data domain (datum): - "quantitative" if the datum is a number - "nominal" if the datum is a string - "temporal" if the datum is a date time object Note: - Data type describes the semantics of the data rather than the primitive data types (number, string, etc.). The same primitive data type can have different types of measurement. For example, numeric data can represent quantitative, ordinal, or nominal data. - Data values for a temporal field can be either a date-time string (e.g., "2015-03-07 12:32:17", "17:01", "2015-03-16". "2015") or a timestamp number (e.g., 1552199579097). - When using with bin, the type property can be either "quantitative" (for using a linear bin scale) or "ordinal" (for using an ordinal bin scale). - When using with timeUnit, the type property can be either "temporal" (default, for using a temporal scale) or "ordinal" (for using an ordinal scale). - When using with aggregate, the type property refers to the post-aggregation data type. For example, we can calculate count distinct of a categorical field "cat" using {"aggregate": "distinct", "field": "cat"}. The "type" of the aggregate output is "quantitative". - Secondary channels (e.g., x2, y2, xError, yError) do not have type as they must have exactly the same type as their primary channels (e.g., x, y). See also: type documentation.

The StrokeDash encoding accepts the following options:

Property	Type	Description
aggregate	Aggregate	Aggregation function for the field (e.g., "mean", "sum", "median", "min", "max", "count"). Default value: undefined (None) See also: aggregate documentation.
band	number	For rect-based marks (rect, bar, and image), mark size relative to bandwidth of band scales, bins or time units. If set to 1, the mark size is set to the bandwidth, the bin interval, or the time unit interval. If set to 0.5, the mark size is half of the bandwidth or the time unit interval. For other marks, relative position on a band of a stacked, binned, time unit or band scale. If set to 0, the marks will be positioned at the beginning of the band. If set to 0.5, the marks will be positioned in the middle of the band.
bin	anyOf(boolean, BinParams, null)	A flag for binning a quantitative field, an object defining binning parameters, or indicating that the data for x or y channel are binned before they are imported into Vega-Lite ("binned"). If true, default binning parameters will be applied. If "binned", this indicates that the data for the x (or y) channel are already binned. You can map the bin-start field to x (or y) and the bin-end field to x2 (or y2). The scale and axis will be formatted similar to binning in Vega-Lite. To adjust the axis ticks based on the bin step, you can also set the axis’s tickMinStep property. Default value: false See also: bin documentation.
condition	anyOf(ConditionalValueDef<(number[]|ExprRef)>, array(ConditionalValueDef<(number[]|ExprRef)>))	One or more value definition(s) with a selection or a test predicate. Note: A field definition’s condition property can only contain conditional value definitions since Vega-Lite only allows at most one encoded field per encoding channel.
field	Field	Required. A string defining the name of the field from which to pull a data value or an object defining iterated values from the repeat operator. See also: field documentation. Notes: 1) Dots (.) and brackets ([ and ]) can be used to access nested objects (e.g., "field": "foo.bar" and "field": "foo['bar']"). If field names contain dots or brackets but are not nested, you can use \\ to escape dots and brackets (e.g., "a\\.b" and "a\\[0\\]"). See more details about escaping in the field documentation. 2) field is not required if aggregate is count.
legend	anyOf(Legend, null)	An object defining properties of the legend. If null, the legend for the encoding channel will be removed. Default value: If undefined, default legend properties are applied. See also: legend documentation.
scale	anyOf(Scale, null)	An object defining properties of the channel’s scale, which is the function that transforms values in the data domain (numbers, dates, strings, etc) to visual values (pixels, colors, sizes) of the encoding channels. If null, the scale will be disabled and the data value will be directly encoded. Default value: If undefined, default scale properties are applied. See also: scale documentation.
sort	Sort	Sort order for the encoded field. For continuous fields (quantitative or temporal), sort can be either "ascending" or "descending". For discrete fields, sort can be one of the following: - "ascending" or "descending" – for sorting by the values’ natural order in JavaScript. - A string indicating an encoding channel name to sort by (e.g., "x" or "y") with an optional minus prefix for descending sort (e.g., "-x" to sort by x-field, descending). This channel string is short-form of a sort-by-encoding definition. For example, "sort": "-x" is equivalent to "sort": {"encoding": "x", "order": "descending"}. - A sort field definition for sorting by another field. - An array specifying the field values in preferred order. In this case, the sort order will obey the values in the array, followed by any unspecified values in their original order. For discrete time field, values in the sort array can be date-time definition objects. In addition, for time units "month" and "day", the values can be the month or day names (case insensitive) or their 3-letter initials (e.g., "Mon", "Tue"). - null indicating no sort. Default value: "ascending" Note: null and sorting by another channel is not supported for row and column. See also: sort documentation.
timeUnit	anyOf(TimeUnit, TimeUnitParams)	Time unit (e.g., year, yearmonth, month, hours) for a temporal field. or a temporal field that gets casted as ordinal. Default value: undefined (None) See also: timeUnit documentation.
title	anyOf(Text, null)	A title for the field. If null, the title will be removed. Default value: derived from the field’s name and transformation function (aggregate, bin and timeUnit). If the field has an aggregate function, the function is displayed as part of the title (e.g., "Sum of Profit"). If the field is binned or has a time unit applied, the applied function is shown in parentheses (e.g., "Profit (binned)", "Transaction Date (year-month)"). Otherwise, the title is simply the field name. Notes: You can customize the default field title format by providing the fieldTitle property in the config or fieldTitle function via the compile function’s options. If both field definition’s title and axis, header, or legend title are defined, axis/header/legend title will be used.
type	StandardType	The type of measurement ("quantitative", "temporal", "ordinal", or "nominal") for the encoded field or constant value (datum). It can also be a "geojson" type for encoding ‘geoshape’. Vega-Lite automatically infers data types in many cases as discussed below. However, type is required for a field if: (1) the field is not nominal and the field encoding has no specified aggregate (except argmin and argmax), bin, scale type, custom sort order, nor timeUnit or (2) if you wish to use an ordinal scale for a field with bin or timeUnit. Default value: For a data field, "nominal" is the default data type unless the field encoding has aggregate, channel, bin, scale type, sort, or timeUnit that satisfies the following criteria: - "quantitative" is the default type if (1) the encoded field contains bin or aggregate except "argmin" and "argmax", (2) the encoding channel is latitude or longitude channel or (3) if the specified scale type is a quantitative scale. - "temporal" is the default type if (1) the encoded field contains timeUnit or (2) the specified scale type is a time or utc scale - ordinal"" is the default type if (1) the encoded field contains a custom sort order, (2) the specified scale type is an ordinal/point/band scale, or (3) the encoding channel is order. For a constant value in data domain (datum): - "quantitative" if the datum is a number - "nominal" if the datum is a string - "temporal" if the datum is a date time object Note: - Data type describes the semantics of the data rather than the primitive data types (number, string, etc.). The same primitive data type can have different types of measurement. For example, numeric data can represent quantitative, ordinal, or nominal data. - Data values for a temporal field can be either a date-time string (e.g., "2015-03-07 12:32:17", "17:01", "2015-03-16". "2015") or a timestamp number (e.g., 1552199579097). - When using with bin, the type property can be either "quantitative" (for using a linear bin scale) or "ordinal" (for using an ordinal bin scale). - When using with timeUnit, the type property can be either "temporal" (default, for using a temporal scale) or "ordinal" (for using an ordinal scale). - When using with aggregate, the type property refers to the post-aggregation data type. For example, we can calculate count distinct of a categorical field "cat" using {"aggregate": "distinct", "field": "cat"}. The "type" of the aggregate output is "quantitative". - Secondary channels (e.g., x2, y2, xError, yError) do not have type as they must have exactly the same type as their primary channels (e.g., x, y). See also: type documentation.

Binning and Aggregation

Beyond simple channel encodings, Altair’s visualizations are built on the concept of the database-style grouping and aggregation; that is, the split-apply-combine abstraction that underpins many data analysis approaches.

For example, building a histogram from a one-dimensional dataset involves splitting data based on the bin it falls in, aggregating the results within each bin using a count of the data, and then combining the results into a final figure.

In Altair, such an operation looks like this:

alt.Chart(cars).mark_bar().encode(
    alt.X('Horsepower', bin=True),
    y='count()'
    # could also use alt.Y(aggregate='count', type='quantitative')
)

Notice here we use the shorthand version of expressing an encoding channel (see Encoding Shorthands) with the count aggregation, which is the one aggregation that does not require a field to be specified.

Similarly, we can create a two-dimensional histogram using, for example, the size of points to indicate counts within the grid (sometimes called a “Bubble Plot”):

alt.Chart(cars).mark_point().encode(
    alt.X('Horsepower', bin=True),
    alt.Y('Miles_per_Gallon', bin=True),
    size='count()',
)

There is no need, however, to limit aggregations to counts alone. For example, we could similarly create a plot where the color of each point represents the mean of a third quantity, such as acceleration:

alt.Chart(cars).mark_circle().encode(
    alt.X('Horsepower', bin=True),
    alt.Y('Miles_per_Gallon', bin=True),
    size='count()',
    color='average(Acceleration):Q'
)

In addition to count and average, there are a large number of available aggregation functions built into Altair; they are listed in the following table:

Aggregate	Description	Example
argmin	An input data object containing the minimum field value.	N/A
argmax	An input data object containing the maximum field value.	N/A
average	The mean (average) field value. Identical to mean.	Line Chart with Layered Aggregates
count	The total count of data objects in the group.	Simple Heatmap
distinct	The count of distinct field values.	N/A
max	The maximum field value.	Boxplot with Min/Max Whiskers
mean	The mean (average) field value.	Interactive Scatter Plot and Linked Layered Histogram
median	The median field value	Boxplot with Min/Max Whiskers
min	The minimum field value.	Boxplot with Min/Max Whiskers
missing	The count of null or undefined field values.	N/A
q1	The lower quartile boundary of values.	Boxplot with Min/Max Whiskers
q3	The upper quartile boundary of values.	Boxplot with Min/Max Whiskers
ci0	The lower boundary of the bootstrapped 95% confidence interval of the mean.	Sorted Error Bars showing Confidence Interval
ci1	The upper boundary of the bootstrapped 95% confidence interval of the mean.	Sorted Error Bars showing Confidence Interval
stderr	The standard error of the field values.	N/A
stdev	The sample standard deviation of field values.	N/A
stdevp	The population standard deviation of field values.	N/A
sum	The sum of field values.	Streamgraph
valid	The count of field values that are not null or undefined.	N/A
values	??	N/A
variance	The sample variance of field values.	N/A
variancep	The population variance of field values.	N/A

Encoding Shorthands

For convenience, Altair allows the specification of the variable name along with the aggregate and type within a simple shorthand string syntax. This makes use of the type shorthand codes listed in Encoding Data Types as well as the aggregate names listed in Binning and Aggregation. The following table shows examples of the shorthand specification alongside the long-form equivalent:

Shorthand	Equivalent long-form
x='name'	alt.X('name')
x='name:Q'	alt.X('name', type='quantitative')
x='sum(name)'	alt.X('name', aggregate='sum')
x='sum(name):Q'	alt.X('name', aggregate='sum', type='quantitative')
x='count():Q'	alt.X(aggregate='count', type='quantitative')

Ordering marks

The order option and Order channel can sort how marks are drawn on the chart.

For stacked marks, this controls the order of components of the stack. Here, the elements of each bar are sorted alphabetically by the name of the nominal data in the color channel.

import altair as alt
from vega_datasets import data

barley = data.barley()

alt.Chart(barley).mark_bar().encode(
    x='variety:N',
    y='sum(yield):Q',
    color='site:N',
    order=alt.Order("site", sort="ascending")
)