doc: add example, interval selection on a map

pyproject.toml

@@ -72,7 +72,8 @@ dev = [
     "types-setuptools",
     "pyarrow>=11",
     "vegafusion[embed]>=1.4.0",
-    "anywidget"
+    "anywidget",
+    "geopandas",
 ]
 doc = [
     "sphinx",
@@ -82,7 +83,6 @@ doc = [
     "numpydoc",
     "pillow>=9,<10",
     "pydata-sphinx-theme>=0.14.1",
-    "geopandas",
     "myst-parser",
     "sphinx_copybutton",
     "sphinx-design",
@@ -216,6 +216,7 @@ module = [
     "yaml.*",
     "vl_convert.*",
     "pandas.lib.*",
+    "geopandas.*",
     "nbformat.*",
     "ipykernel.*",
     "m2r.*",

tests/examples_arguments_syntax/interval_selection_map_quakes.py

@@ -0,0 +1,62 @@
+"""
+Interval Selection on a Map
+===========================
+
+This is an example of a binned bar chart on the right where the filtered overlay
+is adjusted by interacting with the map on the left.
+"""
+# category: interactive charts
+import altair as alt
+from vega_datasets import data
+import geopandas as gpd
+
+# load data
+gdf_quakies = gpd.read_file(data.earthquakes.url, driver="GeoJSON")
+gdf_world = gpd.read_file(data.world_110m.url, driver="TopoJSON")
+
+# defintion for interactive brush
+brush = alt.selection_interval(
+    encodings=["longitude"], 
+    empty=False, 
+    value={"longitude": [-50, -110]}
+)
+
+# world disk
+sphere = alt.Chart(alt.sphere()).mark_geoshape(
+    fill="transparent", stroke="lightgray", strokeWidth=1
+)
+
+# countries as shapes
+world = alt.Chart(gdf_world).mark_geoshape(
+    fill="lightgray", stroke="white", strokeWidth=0.1
+)
+
+# earthquakes as dots on map
+quakes = alt.Chart(gdf_quakies).transform_calculate(
+    lon="datum.geometry.coordinates[0]",
+    lat="datum.geometry.coordinates[1]",
+).mark_circle(opacity=0.35, tooltip=True).encode(
+    longitude="lon:Q",
+    latitude="lat:Q",
+    color=alt.condition(brush, alt.value("goldenrod"), alt.value("steelblue")),
+    size=alt.Size("mag:Q", scale=alt.Scale(type="pow", range=[1, 1000], domain=[0, 7], exponent=4)),
+).add_params(brush)
+
+# combine layers for the map
+left_map = alt.layer(sphere, world, quakes).project(type="mercator") 
+
+# histogram of binned earthquakes
+bars = alt.Chart(gdf_quakies).mark_bar().encode(
+    x=alt.X("mag:Q").bin(extent=[0,7]),
+    y="count(mag):Q",
+    color=alt.value("steelblue")
+)
+
+# filtered earthquakes
+bars_overlay = bars.encode(color=alt.value("goldenrod")).transform_filter(brush)
+
+# combine layers for histogram
+right_bars = alt.layer(bars, bars_overlay)
+
+# vertical concatenate map and bars
+left_map | right_bars

tests/examples_methods_syntax/interval_selection_map_quakes.py

@@ -0,0 +1,62 @@
+"""
+Interval Selection on a Map
+===========================
+
+This is an example of a binned bar chart on the right where the filtered overlay
+is adjusted by interacting with the map on the left.
+"""
+# category: interactive charts
+import altair as alt
+from vega_datasets import data
+import geopandas as gpd
+
+# load data
+gdf_quakies = gpd.read_file(data.earthquakes.url, driver="GeoJSON")
+gdf_world = gpd.read_file(data.world_110m.url, driver="TopoJSON")
+
+# defintion for interactive brush
+brush = alt.selection_interval(
+    encodings=["longitude"], 
+    empty=False, 
+    value={"longitude": [-50, -110]}
+)
+
+# world disk
+sphere = alt.Chart(alt.sphere()).mark_geoshape(
+    fill="transparent", stroke="lightgray", strokeWidth=1
+)
+
+# countries as shapes
+world = alt.Chart(gdf_world).mark_geoshape(
+    fill="lightgray", stroke="white", strokeWidth=0.1
+)
+
+# earthquakes as dots on map
+quakes = alt.Chart(gdf_quakies).transform_calculate(
+    lon="datum.geometry.coordinates[0]",
+    lat="datum.geometry.coordinates[1]",
+).mark_circle(opacity=0.35, tooltip=True).encode(
+    longitude="lon:Q",
+    latitude="lat:Q",
+    color=alt.condition(brush, alt.value("goldenrod"), alt.value("steelblue")),
+    size=alt.Size("mag:Q").scale(type="pow", range=[1, 1000], domain=[0, 7], exponent=4),
+).add_params(brush)
+
+# combine layers for the map
+left_map = alt.layer(sphere, world, quakes).project(type="mercator") 
+
+# histogram of binned earthquakes
+bars = alt.Chart(gdf_quakies).mark_bar().encode(
+    x=alt.X("mag:Q").bin(extent=[0,7]),
+    y="count(mag):Q",
+    color=alt.value("steelblue")
+)
+
+# filtered earthquakes
+bars_overlay = bars.encode(color=alt.value("goldenrod")).transform_filter(brush)
+
+# combine layers for histogram
+right_bars = alt.layer(bars, bars_overlay)
+
+# vertical concatenate map and bars
+left_map | right_bars