docs: Adds altair_theme_test.py

Related: #3519 (comment)

tests/altair_theme_test.py

@@ -0,0 +1,148 @@
+import polars as pl
+
+import altair as alt
+from vega_datasets import data
+
+common_data = pl.DataFrame(
+    [
+        {"Index": 1, "Value": 28, "Position": 1, "Category": "A"},
+        {"Index": 2, "Value": 55, "Position": 2, "Category": "A"},
+        {"Index": 3, "Value": 43, "Position": 3, "Category": "A"},
+        {"Index": 4, "Value": 91, "Position": 4, "Category": "A"},
+        {"Index": 5, "Value": 81, "Position": 5, "Category": "A"},
+        {"Index": 6, "Value": 53, "Position": 6, "Category": "A"},
+        {"Index": 7, "Value": 19, "Position": 1, "Category": "B"},
+        {"Index": 8, "Value": 87, "Position": 2, "Category": "B"},
+        {"Index": 9, "Value": 52, "Position": 3, "Category": "B"},
+        {"Index": 10, "Value": 48, "Position": 4, "Category": "B"},
+        {"Index": 11, "Value": 24, "Position": 5, "Category": "B"},
+        {"Index": 12, "Value": 49, "Position": 6, "Category": "B"},
+        {"Index": 13, "Value": 87, "Position": 1, "Category": "C"},
+        {"Index": 14, "Value": 66, "Position": 2, "Category": "C"},
+        {"Index": 15, "Value": 17, "Position": 3, "Category": "C"},
+        {"Index": 16, "Value": 27, "Position": 4, "Category": "C"},
+        {"Index": 17, "Value": 68, "Position": 5, "Category": "C"},
+        {"Index": 18, "Value": 16, "Position": 6, "Category": "C"},
+    ]
+)
+
+
+bar = (
+    alt.Chart(common_data, title="Bar", width=480, height=150)
+    .mark_bar()
+    .encode(x=alt.X("Index:O").axis(offset=1), y=alt.Y("Value:Q"), tooltip="Value:Q")
+)
+
+line = (
+    alt.Chart(common_data, width=240, height=150, title="Line")
+    .mark_line()
+    .encode(
+        x=alt.X("Position").axis(grid=False),
+        y=alt.Y("Value:Q").axis(grid=False),
+        color=alt.Color("Category").legend(None),
+        tooltip=["Index", "Value", "Position", "Category"],
+    )
+)
+
+point_shape = (
+    alt.Chart(common_data, width=200, height=200, title="Point (Shape)")
+    .mark_point()
+    .encode(
+        x=alt.X("Position:O").axis(grid=False),
+        y=alt.Y("Value:Q").axis(grid=False),
+        shape=alt.Shape("Category").legend(None),
+        color=alt.Color("Category").legend(None),
+        tooltip=["Index", "Value", "Position", "Category"],
+    )
+)
+
+bar_facet = (
+    alt.Chart(data.barley(), width=220, title=alt.Title("Bar (Facet)", anchor="middle"))
+    .mark_bar(tooltip=True)
+    .encode(column="year:O", x="yield", y="variety", color="site")
+)
+
+rect_heatmap = (
+    alt.Chart(
+        data.seattle_weather(),
+        title=alt.Title(
+            "Rect (Heatmap)", subtitle="Daily Max Temperatures (C) in Seattle, WA"
+        ),
+        height=200,
+    )
+    .mark_rect()
+    .encode(
+        x=alt.X("date(date):O").title("Day").axis(format="%e", labelAngle=0),
+        y=alt.Y("month(date):O").title("Month"),
+        color=alt.Color("max(temp_max)").title(None),
+        tooltip=[
+            alt.Tooltip("monthdate(date)", title="Date"),
+            alt.Tooltip("max(temp_max)", title="Max Temp"),
+        ],
+    )
+)
+
+geoshape = (
+    alt.Chart(
+        alt.topo_feature(data.us_10m.url, "counties"),
+        title=alt.Title("Geoshape", subtitle="Unemployment rate per county"),
+        width=500,
+        height=300,
+    )
+    .mark_geoshape(tooltip=True)
+    .encode(color="rate:Q")
+    .transform_lookup(
+        lookup="id",
+        from_=alt.LookupData(data.unemployment.url, "id", ["rate"]),  # pyright: ignore[reportArgumentType]
+    )
+    .project(type="albersUsa")
+)
+
+point = (
+    alt.Chart(data.movies.url, height=250, width=250, title="Point")
+    .mark_point()
+    .transform_filter(alt.datum["IMDB_Rating"] != None)  # noqa: E711
+    .transform_filter(
+        alt.FieldRangePredicate("Release_Date", [None, 2019], timeUnit="year")
+    )
+    .transform_joinaggregate(Average_Rating="mean(IMDB_Rating)")
+    .transform_calculate(
+        Rating_Delta=alt.datum["IMDB_Rating"] - alt.datum.Average_Rating
+    )
+    .encode(
+        x=alt.X("Release_Date:T").title("Release Date"),
+        y=alt.Y("Rating_Delta:Q").title("Rating Delta"),
+        color=alt.Color("Rating_Delta:Q").title("Rating Delta").scale(domainMid=0),
+    )
+)
+
+area = (
+    alt.Chart(data.iowa_electricity(), title="Area", height=250, width=250)
+    .mark_area(tooltip=True)
+    .encode(
+        alt.X("year:T").title("Year"),
+        alt.Y("net_generation:Q")
+        .title("Share of net generation")
+        .stack("normalize")
+        .axis(format=".0%"),
+        alt.Color("source:N").title("Electricity source"),
+    )
+)
+
+
+alt_theme_test = (
+    (bar | line)
+    & (point_shape | bar_facet).resolve_scale(color="independent")
+    & (point | area)
+    & rect_heatmap
+    & geoshape
+).properties(
+    title=alt.Title(
+        "Vega-Altair Theme Test",
+        fontSize=20,
+        subtitle="Adapted from https://vega.github.io/vega-themes/",
+        offset=16,
+    )
+)
+
+alt_theme_test  # noqa: B018