DOC: Improved barley case study
"""
Becker's Barley Trellis Plot
----------------------------
-This example shows how to make a Trellis Plot with the barley dataset.
+The example demonstrates the trellis charts created by Richard Becker, William Cleveland and others in the 1990s. Using the visualization technique below they identified an anomoly in a widely used agriculatural dataset, which they termed ["The Morris Mistake."](https://www.albany.edu/acc/courses/acc522fall2007/lecturenotes/trellis.usermanual.pdf). It became their favored way of showcasing the power of their pioneering plot.
"""
# category: case studies
import altair as alt
@@ -9,13 +9,22 @@ from vega_datasets import data
source = data.barley()
-alt.Chart(source).mark_point().encode(
- alt.X('median(yield)', scale=alt.Scale(zero=False)),
+alt.Chart(source, title="The Morris Mistake").mark_point().encode(
+ alt.X(
+ 'yield',
+ scale=alt.Scale(zero=False),
+ axis=alt.Axis(grid=False, title="Barley Yield (bushels/acre)")
+ ),
alt.Y(
'variety',
- sort=alt.EncodingSortField(field='yield', op='median', order='descending'),
- scale=alt.Scale(rangeStep=20)
+ sort=alt.EncodingSortField(field='yield', op='sum', order='descending'),
+ scale=alt.Scale(rangeStep=20),
+ axis=alt.Axis(title="", grid=True)
),
- color='year:N',
- row='site'
+ color=alt.Color('year:N', legend=alt.Legend(title="Year")),
+ row=alt.Row(
+ 'site',
+ title="",
+ sort=alt.EncodingSortField(field='yield', op='sum', order='descending'),
+ )
)
