docs: Adds example Calculate Residuals

tests/examples_arguments_syntax/calculate_residuals.py

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+"""
+Calculate Residuals
+-------------------
+A dot plot showing each movie in the database, and the difference from the average movie rating.
+The display is sorted by year to visualize everything in sequential order. 
+The graph is for all Movies before 2019.
+
+Adapted from `Calculate Residuals <https://vega.github.io/vega-lite/examples/joinaggregate_residual_graph.html>`_.
+"""
+# category: advanced calculations
+
+import altair as alt
+from vega_datasets import data
+
+imdb_rating = alt.datum["IMDB_Rating"]
+source = data.movies.url
+
+chart = (
+    alt.Chart(source)
+    .mark_point()
+    .transform_filter(imdb_rating != None)
+    .transform_filter(
+        alt.FieldRangePredicate("Release_Date", [None, 2019], timeUnit="year")
+    )
+    .transform_joinaggregate(Average_Rating="mean(IMDB_Rating)")
+    .transform_calculate(Rating_Delta=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=alt.Scale(domainMid=0),
+        ),
+    )
+)
+chart

tests/examples_methods_syntax/calculate_residuals.py

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+"""
+Calculate Residuals
+-------------------
+A dot plot showing each movie in the database, and the difference from the average movie rating.
+The display is sorted by year to visualize everything in sequential order. 
+The graph is for all Movies before 2019.
+
+Adapted from `Calculate Residuals <https://vega.github.io/vega-lite/examples/joinaggregate_residual_graph.html>`_.
+"""
+# category: advanced calculations
+
+import altair as alt
+from vega_datasets import data
+
+imdb_rating = alt.datum["IMDB_Rating"]
+source = data.movies.url
+
+chart = (
+    alt.Chart(source)
+    .mark_point()
+    .transform_filter(imdb_rating != None)
+    .transform_filter(
+        alt.FieldRangePredicate("Release_Date", [None, 2019], timeUnit="year")
+    )
+    .transform_joinaggregate(Average_Rating="mean(IMDB_Rating)")
+    .transform_calculate(Rating_Delta=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),
+    )
+)
+chart