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"""
Wheat and Wages
---------------
A recreation of William Playfair's classic chart visualizing
the price of wheat, the wages of a mechanic, and the reigning British monarch.
This is a more polished version of the simpler chart in :ref:`gallery_bar_and_line_with_dual_axis`.
"""
# category: case studies
import altair as alt
from vega_datasets import data
base_wheat = alt.Chart(data.wheat.url).transform_calculate(
year_end="+datum.year + 5")
base_monarchs = alt.Chart(data.monarchs.url).transform_calculate(
offset="((!datum.commonwealth && datum.index % 2) ? -1: 1) * 2 + 95",
off2="((!datum.commonwealth && datum.index % 2) ? -1: 1) + 95",
y="95",
x="+datum.start + (+datum.end - +datum.start)/2"
)
bars = base_wheat.mark_bar(**{"fill": "#aaa", "stroke": "#999"}).encode(
x=alt.X("year:Q", axis=alt.Axis(format='d', tickCount=5)),
y=alt.Y("wheat:Q", axis=alt.Axis(zindex=1)),
x2=alt.X2("year_end")
)
area = base_wheat.mark_area(**{"color": "#a4cedb", "opacity": 0.7}).encode(
x=alt.X("year:Q"),
y=alt.Y("wages:Q")
)
area_line_1 = area.mark_line(**{"color": "#000", "opacity": 0.7})
area_line_2 = area.mark_line(**{"yOffset": -2, "color": "#EE8182"})
top_bars = base_monarchs.mark_bar(stroke="#000").encode(
x=alt.X("start:Q"),
x2=alt.X2("end"),
y=alt.Y("y:Q"),
y2=alt.Y2("offset"),
fill=alt.Fill("commonwealth:N", legend=None, scale=alt.Scale(range=["black", "white"]))
)
top_text = base_monarchs.mark_text(**{"yOffset": 14, "fontSize": 9, "fontStyle": "italic"}).encode(
x=alt.X("x:Q"),
y=alt.Y("off2:Q"),
text=alt.Text("name:N")
)
(bars + area + area_line_1 + area_line_2 + top_bars + top_text).properties(
width=900, height=400
).configure_axis(
title=None, gridColor="white", gridOpacity=0.25, domain=False
).configure_view(
stroke="transparent"
)
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