(DOCSP-11785): Add Top Item chart (#408)

* (DOCSP-11785): Add Top Item chart

* edits per review

Author: jeff-allen-mongo

source/chart-type-reference/text-charts.txt

@@ -16,3 +16,4 @@ Text Charts
       /chart-type-reference/data-table
       /chart-type-reference/number-chart
       /chart-type-reference/word-cloud
+      /chart-type-reference/top-item

source/chart-type-reference/top-item.txt

@@ -0,0 +1,93 @@
+.. _top-item-ref:
+
+==============
+Top Item Chart
+==============
+
+.. default-domain:: mongodb
+
+.. contents:: On this page
+   :local:
+   :backlinks: none
+   :depth: 1
+   :class: singlecol
+
+Top Item charts show information from the document with the
+greatest or smallest value for a specified field.
+
+When you create a Top Item chart, you specify:
+
+- The field by which to sort your collection.
+
+- Whether you want to sort in ascending or descending order.
+
+- The fields you want to display from the first document returned by
+  your specified sort.
+
+Encoding Channels
+-----------------
+
+Top Item charts utilize the following :ref:`encoding channels
+<encoding-channels>`:
+
+.. list-table::
+   :header-rows: 1
+   :widths: 20 80
+
+   * - Encoding Channel
+     - Description
+
+   * - Sort
+     - The field by which to sort the collection. You can specify an
+       ascending or descending sort.
+
+   * - Display
+     - The fields to display from the top item in the collection after
+       sorting.
+       
+.. note::
+
+   You cannot perform aggregations on :guilabel:`Display`
+   fields. 
+
+Use Cases
+---------
+
+Use Top Item charts to show information about the most extreme or most
+recent instance of a particular field value. For example, you can use
+Top Item charts to show information on:
+
+- The most recent reading from a collection of sensor data, such as
+  temperature readings.
+
+- The highest rated movie in a collection.
+
+- The cheapest available room in a collection of available hotel
+  listings.
+
+- The largest sale recorded in the past month (when combining a Top
+  Item chart with :ref:`date filters <charts-filter-documents>`).
+
+Example
+-------
+
+The following chart uses a data source containing :atlas:`Sample AirBnB
+Listing </sample-data/sample-airbnb/>` data and shows information on the
+document with the highest ``monthly_price`` in the collection:
+
+.. figure:: /images/charts/top-item-example.png
+   :figwidth: 700px
+   :alt: Top Item Chart with AirBnB Data
+
+The chart sorts the documents based on ``monthly_price`` in
+descending order, and returns the first document appearing in the sort.
+
+The chart displays the following fields:
+
+- ``monthly_price``
+
+- ``property_type``
+
+- ``country``
+
+- ``suburb``

source/chart-types.txt

@@ -82,6 +82,16 @@ keywords and phrases.
 .. figure:: /images/charts/word-cloud-small.png
    :figwidth: 525px
 
+:ref:`Top Item Charts <top-item-ref>`
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Top Item charts display information from the document with the greatest
+or smallest value for a specified field.
+
+.. figure:: /images/charts/top-item-small.png
+   :figwidth: 525px
+   :alt: Example Top Item Chart
+
 :ref:`Geospatial Charts <geo-spatial>`
 --------------------------------------