Becker’s Barley Wrapped Facet Plot

The example demonstrates the faceted charts created by Richard Becker, William Cleveland and others in the 1990s. Using the visualization technique where each row is a different site (i.e. the chart is faceted by site), they identified an anomaly in a widely used agriculatural dataset, where the “Morris” site accidentally had the years 1931 and 1932 swapped. They named this “The Morris Mistake.”.

Method syntax

import altair as alt
from vega_datasets import data

source = data.barley.url

alt.Chart(source).mark_point().encode(
    alt.X("median(yield):Q").scale(zero=False),
    y="variety:O",
    color="year:N",
    facet=alt.Facet("site:O", columns=2),
).properties(
    width=200,
    height=100,
)

Attribute syntax

import altair as alt
from vega_datasets import data

source = data.barley.url

alt.Chart(source).mark_point().encode(
    alt.X("median(yield):Q", scale=alt.Scale(zero=False)),
    y="variety:O",
    color="year:N",
    facet=alt.Facet("site:O", columns=2),
).properties(
    width=200,
    height=100,
)