Add Spatial Expression Column - Average

The Average option averages the values of an expression on one Overlay whose origin is within a Polygon on the current Overlay.

Open the Spatial expression type dialog (see Add Spatial Expression for information)

Click Average to open the configuration dialog. Here you can see the overlays in the SWD:

The following example assumes an SWD with Polygon Items on each of three overlays:

In this case the Spatial expression configuration dialog will be displayed as below:

Select the Overlay to search for Items and the schema columns from which to calculate the average.

Option	Description
Column name	This is the default name of the results column which will be created in the table. This is editable.
MapTip/Prefix/Hidden	Controls the manner in which the data is displayed on the graphics. See Map Tips.
Expression	Shows the spatial expression being used to create the results.

In this example select Overlay 2.

Click Finish.

The result will be added as a column to the Table View:

This result shows the average of areas of Items on Overlay 2 which are within a Polygon on Overlay 1, in this case it returns an Average of Area on Overlay 2 of 140.

If you carry out this procedure again but this time selecting Overlay 3 in the Spatial expression configuration dialog the following result will be shown:

This result shows the average of areas of Items on Overlay 3 which are within a Polygon on Overlay 1, in this case it returns an Average of Area on Overlay 3 of 37 and 77.

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