DOC: remove obsolete compound charts data section
@@ -373,79 +373,3 @@ the column.
Though each of the above examples have faceted the data across columns,
faceting across rows (or across rows *and* columns) is supported as
well.
\ No newline at end of file
-
-
-.. _compound-charts-data:
-
-Advanced: Compound Charts, Data, and Transforms
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-When using compound charts, it is possible to specify data in multiple places,
-and if you are using large datasets it can be pertinent to think about where
-you specify data.
-
-For example, suppose you are creating a layered plot with a dataset marked by
-both points and lines:
-
-.. altair-plot::
- :chart-var-name: chart
-
- import altair as alt
- import pandas as pd
-
- data = pd.DataFrame({'x': range(10)})
-
- base = alt.Chart(data).transform_calculate(
- y='sin(datum.x)'
- ).encode(
- x='x:Q',
- y='y:Q'
- )
-
- chart = base.mark_point() + base.mark_line()
-
-If you examine the JSON specification generated by this chart, you see that
-both the data reference and the transform are specified twice, once per layer.
-
-.. altair-plot::
- :output: stdout
-
- from pprint import pprint
- pprint(chart.to_dict())
-
-This happens because each layer of the chart is constructed from a copy of
-the ``base`` object we created, which contains its own data and transform.
-
-In the compound charts created by methods discussed in this section, sub-charts
-are aware of the data and transforms defined by their parent objects, and so
-you can create cleaner specifications by defining them just once at the
-top level. For layered charts, even the encodings can be specified at the
-top level:
-
-.. altair-plot::
- :chart-var-name: chart
-
- chart = alt.LayerChart(data).transform_calculate(
- y='sin(datum.x)'
- ).encode(
- x='x:Q',
- y='y:Q'
- )
-
- chart += alt.Chart().mark_point()
- chart += alt.Chart().mark_line()
-
-When the chart is created this way, the spec contains only one copy of the
-data, transform, and encodings, which leads to a more efficient chart
-representation:
-
-.. altair-plot::
- :output: stdout
-
- pprint(chart.to_dict())
-
-Comparing this to the identically-rendered specification above, we see that
-there is much less duplication of information.
-
-This should not make any significant difference in chart behavior or
-performance, but for the advanced user it is useful to keep these
-features in mind.
