(DOCSP-13974) Line smoothing (#456)

* (DOCSP-13974) Line smoothing

* add step examples

Author: zach-carr

source/chart-type-reference/line-area-chart.txt

@@ -268,6 +268,43 @@ Add a Trendline
 
 .. include:: /includes/customization/trendline.rst
 
+Smooth Lines
+~~~~~~~~~~~~
+
+You can change the way lines are drawn on your chart. To smooth lines:
+
+1. Open the :ref:`Customize <customize-charts>` pane for your chart.
+
+#. In the :guilabel:`General Customization` section, set
+   :guilabel:`Line Smoothing` to the desired option.
+
+The following line smoothing options are available:
+
+.. list-table::
+   :header-rows: 1
+   :stub-columns: 1
+   :widths: 30 70
+
+   * - Option
+     - Description
+
+   * - None (Default)
+     - Draws straight lines between data points.
+
+   * - Smooth
+     - Draws curved lines between data points.
+
+   * - Step Before
+     - Lines extend horizontally to data points. This is useful 
+       for visualizing data that only changes in intervals and is 
+       collected at the end of a period, such as 
+       daily average temperature.
+
+   * - Step After
+     - Lines extend horizontally from data points. This is useful 
+       for visualizing data that only changes in intervals, such as 
+       stock prices.
+
 Examples
 --------