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 altair.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 altair.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,
)