Null values are shown on the chart as empty spaces or gaps between data points in a series. In Reporting Services paginated reports, empty points are data points that can be inserted in the empty space created by null values.
By default, empty points are calculated by taking the average of the previous and next data points that contain a value. You can change this so that all empty points are inserted at zero.
For more information, see Empty and Null Data Points in Charts (Report Builder and SSRS).
You can create and modify paginated report definition (.rdl) files in Report Builder and in Report Designer in SQL Server Data Tools. Each authoring environment provides different ways to create, open, and save reports and related items.
To specify empty points on a chart
Open the Properties pane.
On the design surface, right-click the series that contains null values. The properties for the series are displayed in the Properties pane.
Expand the EmptyPoint node.
Select a color value for the Color property.
In the EmptyPoint node, expand the Marker node.
Select a marker type for the MarkerType property.
You must select a marker type to add empty points to a bar, column or scatter chart. However, for area, line and radar charts, selecting a marker type is optional because the chart fills in the empty space or gap without requiring a marker to be specified.
Set the value of the empty point.
In the Properties pane, expand the CustomAttributes node.
Set the EmptyPointValue property. To insert empty points at an average of the previous and next data points, select Average. To insert empty points at zero, select Zero.
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Charts (Report Builder and SSRS)