add example

tests/examples_arguments_syntax/interval_selection_map_quakes.py

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+"""
+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

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+"""
+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