Horizontal stacked bars

Compare barley yields by variety, with each growing site shown as a segment.

Each bar shows a barley variety’s total yield. Colored segments show the contribution from each growing site; the horizontal legend identifies them.

Data use and provenance

The barley table is loaded from the versioned Vega datasets collection. GenomeSpy sums yields by variety and site, then stacks the totals in the browser.

Adapted from the official GenomeSpy example.

Code

"""Horizontal stacked bars.

Compare barley yields by variety, with each growing site shown as a segment.
"""

import genome_spy as gs


# Load the same barley table used by the upstream example.
data = gs.Data(url="https://cdn.jsdelivr.net/npm/vega-datasets@2.9.0/data/barley.json")

chart = (
    gs.Chart(data)
    # Sum the years for each site, then place the site totals side by side.
    .transform_aggregate(
        groupby=["variety", "site"], fields=["yield"], ops=["sum"], as_=["yieldSum"]
    )
    .transform_stack(
        field="yieldSum",
        groupby=["variety"],
        sort=gs.compare("site"),
        as_=["yieldStart", "yieldEnd"],
    )
    .mark_rect()
    .encode(
        x=gs.X("yieldStart:Q").title("Sum of yield"),
        x2=gs.X2("yieldEnd"),
        y=gs.Y("variety:N").scale(padding=0.1),
        color=gs.Color("site:N"),
    )
    .configure_legend(disable=False, orient="bottom", direction="horizontal", offset=18)
    .properties(background="#fafafa")
)

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