Merge pull request #2628 from palewire/patch-5

Tidy up U.S. Population by Age and Sex case study

altair/examples/us_population_over_time.py

@@ -1,6 +1,6 @@
 """
-US Population Over Time
-=======================
+US Population by Age and Sex
+============================
 This chart visualizes the age distribution of the US population over time.
 It uses a slider widget that is bound to the year to visualize the age
 distribution over time.
@@ -11,21 +11,23 @@
 
 source = data.population.url
 
-pink_blue = alt.Scale(domain=('Male', 'Female'),
-                      range=["steelblue", "salmon"])
-
-slider = alt.binding_range(min=1900, max=2000, step=10)
-select_year = alt.selection_single(name="year", fields=['year'],
-                                   bind=slider, init={'year': 2000})
+select_year = alt.selection_single(
+    name="Year",
+    fields=["year"],
+    bind=alt.binding_range(min=1900, max=2000, step=10, name="Year"),
+    init={"year": 2000},
+)
 
 alt.Chart(source).mark_bar().encode(
-    x=alt.X('sex:N', title=None),
-    y=alt.Y('people:Q', scale=alt.Scale(domain=(0, 12000000))),
-    color=alt.Color('sex:N', scale=pink_blue),
-    column='age:O'
-).properties(
-    width=20
-).add_selection(
+    x=alt.X("sex:N", axis=alt.Axis(labels=False, title=None, ticks=False)),
+    y=alt.Y("people:Q", scale=alt.Scale(domain=(0, 12000000)), title="Population"),
+    color=alt.Color(
+        "sex:N",
+        scale=alt.Scale(domain=("Male", "Female"), range=["steelblue", "salmon"]),
+        title="Sex",
+    ),
+    column=alt.Column("age:O", title="Age"),
+).properties(width=20, title="U.S. Population by Age and Sex").add_selection(
     select_year
 ).transform_calculate(
     "sex", alt.expr.if_(alt.datum.sex == 1, "Male", "Female")