Point

point mark represents each data point with a symbol. Point marks are commonly used in visualizations like scatter plots.

Point Mark Properties

Click to show code

import altair as alt
from vega_datasets import data

source = data.cars()

shape_select = alt.binding_select(
    options=[
        "arrow",
        "circle",
        "square",
        "cross",
        "diamond",
        "triangle",
        "triangle-up",
        "triangle-down",
        "triangle-right",
        "triangle-left",
        "wedge",
        "stroke",
        "M-1,-1H1V1H-1Z",
        "M0,.5L.6,.8L.5,.1L1,-.3L.3,-.4L0,-1L-.3,-.4L-1,-.3L-.5,.1L-.6,.8L0,.5Z",
    ],
    name="shape",
)
shape_var = alt.param(bind=shape_select, value="circle")

angle_slider = alt.binding_range(min=-360, max=360, step=1, name="angle")
angle_var = alt.param(bind=angle_slider, value=0)

size_slider = alt.binding_range(min=0, max=500, step=10, name="size")
size_var = alt.param(bind=size_slider, value=50)

strokeWidth_slider = alt.binding_range(min=0, max=10, step=0.5, name="strokeWidth")
strokeWidth_var = alt.param(bind=strokeWidth_slider, value=2)

alt.Chart(source).mark_point(
    shape=shape_var,
    angle=angle_var,
    size=size_var,
    strokeWidth=strokeWidth_var,
).encode(x="Horsepower:Q", y="Miles_per_Gallon:Q").add_params(
    shape_var, angle_var, size_var, strokeWidth_var
)

A point mark definition can contain any standard mark properties and the following special properties:

Click to show table

Property	Type	Description
shape	anyOf(anyOf(SymbolShape, string), ExprRef)	Shape of the point marks. Supported values include: plotting shapes: "circle", "square", "cross", "diamond", "triangle-up", "triangle-down", "triangle-right", or "triangle-left". the line symbol "stroke" centered directional shapes "arrow", "wedge", or "triangle" a custom SVG path string (For correct sizing, custom shape paths should be defined within a square bounding box with coordinates ranging from -1 to 1 along both the x and y dimensions.) Default value: "circle"
size	anyOf(number, ExprRef)	Default size for marks. For point/circle/square, this represents the pixel area of the marks. Note that this value sets the area of the symbol; the side lengths will increase with the square root of this value. For bar, this represents the band size of the bar, in pixels. For text, this represents the font size, in pixels. Default value: 30 for point, circle, square marks; width/height’s step 2 for bar marks with discrete dimensions; 5 for bar marks with continuous dimensions; 11 for text marks.

Examples

Dot Plot

Mapping a field to either only x or only y of point marks creates a dot plot.

import altair as alt
from vega_datasets import data

source = data.movies()
alt.Chart(source).mark_point().encode(
    x="IMDB_Rating:Q"
)