(DOCSP-11995): Sort multi-series chart by specifed series (#409)

* (DOCSP-11995): Sort multi-series chart by specifed series

* Updates per review

Author: jeff-allen-mongo

source/bin-data.txt

@@ -268,15 +268,50 @@ chart type:
 Sort Data
 ---------
 
-By default, |charts-short| sorts data based on the :guilabel:`Value`
-field in descending order.
+Use the :guilabel:`Sort By` dropdown in the Chart Builder to sort
+chart data by either:
 
-Use the :guilabel:`Sort By` dropdown in the Chart Builder to sort by
-either the :guilabel:`Category` field or aggregated value.
+- Category
+- Value
+- Series field (for :ref:`multi-series charts <multi-series-charts>`)
+
+If you sort a multi-series chart generically by :guilabel:`Value`
+without sorting by a specific series, |charts| sorts your data based on
+the sum of all values in your series.
 
 To toggle between ascending or descending sort order, click the ``a-z``
 button to the right of the :guilabel:`Sort By` dropdown.
 
+By default, |charts-short| sorts data based on :guilabel:`Value`
+in descending order.
+
+Sort Multi-Series Charts by Series Value
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+If you create a :ref:`multi-series chart <multi-series-charts>` using a
+different field per series, you can sort the chart by a specific series
+field.
+
+.. example::
+
+   The following charts use the :ref:`Sample Data: Movies <sample-data>`
+   data source to compare the mean number of ``fresh`` and ``rotten``
+   Rotten Tomato ratings for movies in each genre.
+
+   This chart is sorted by the mean ``fresh`` value in descending
+   order:
+
+   .. figure:: /images/charts/sort-by-series-fresh-desc.png
+      :figwidth: 550px
+      :alt: Chart sorted by fresh rating in descending order
+
+   This chart is sorted by the mean ``rotten`` value in ascending
+   order:
+
+   .. figure:: /images/charts/sort-by-series-rotten-asc.png
+      :figwidth: 550px
+      :alt: Chart sorted by rotten rating in ascending order
+   
 .. _charts-limit-data:
 
 Limit Data

source/images/charts/sort-by-series-fresh-desc.png

@@ -17,7 +17,7 @@ chart data into groups, or *series*, to compare additional
 fields within your schema. There are two ways to create multi-series
 charts:
 
-- :ref:`Using multiple aggregation or value field mappings
+- :ref:`Map Multiple Fields to a Single Axis
   <multiple-field-mappings>`. Use this method to compare or aggregate
   upon multiple non-categorical fields in the schema.
 
@@ -27,15 +27,14 @@ charts:
 
 .. _multiple-field-mappings:
 
-Multiple Field Mappings to a Single Axis
-----------------------------------------
+Map Multiple Fields to a Single Axis
+------------------------------------
 
 |charts| allows you to map multiple :ref:`Aggregation
-<building-charts-aggregation>` or :guilabel:`Value`
-:ref:`encoding channels <encoding-channels>` to a single chart property
-(such as the :guilabel:`X Axis` or :guilabel:`Y Axis`). This allows you
-to compare additional fields in your visualization by creating new
-series based on the encoding channels added.
+<building-charts-aggregation>` or :guilabel:`Value` fields to a single
+chart property (such as the :guilabel:`X Axis` or :guilabel:`Y Axis`).
+This allows you to compare additional fields by creating new series
+based on the encoding channels added.
 
 After dragging a field to an :guilabel:`aggregation`
 or :guilabel:`value` :ref:`encoding channel <encoding-channels>`, an