ColumnAggregate()

Summary

Performs a geographic overlay between two layers and aggregates tabular data.

 

Syntax

ColumnAggregate(string layer_set, real buffer, string source_layer_set, array fields, array options)

 

Argument	Contents
layer_set	The layer and set into which data are aggregated (the target layer)
buffer	The size of the buffer to construct around each feature in layer_set
source_layer_set	The layer and selection set from which data are aggregated
fields	An array containing one element for each field in the output table. Each element is an array of four items that indicates the statistic calculated, as shown below

 

Element	Type	Contents
1	String	The name of an existing field in the target layer in which the result is stored
2	String	Statistic: "SUM", "MIN", "MAX", "DOM" (DOMINANT), "AVG" (AVERAGE), "STDDEV" or "COUNT"
3	String	The name of the source data field in the source layer
4	String	An optional element indicating a weighting field to use from the source layer

 

No options are currently supported.

 

Notes

• The COUNT statistic computes the number of features in the source layer that are within or touching the buffer area around the feature in the target layer.

• The DOM (dominant) statistic chooses any non-missing value from the source layer.

• The fields in the target layer can include any mappable field.

• When a row for a source field is null, a missing value is returned.

• The optional weighting field is used only for the AVG statistic, and ignored for all other statistics.

• The source layer can be joined to more than one data set, as long as it is a cascading join; for example, if the source layer is A, you can join A to B and then join A+B to C.  You cannot join A to B and then A to C (a non-cascading join). Use the source layer name, not the joined view name, when you reference the source layer.

• The target layer, if it is a joined view, cannot have fields with the same name.

Example

// Before running the example, create a map by opening manh_zip.cdf and add the

// layer manhtrct.cdf, both in the Tutorial folder.

// Then set the working layer to Tract, and use the Dataview-Modify

// Table command to add a field Black of type Real.

ColumnAggregate("Tract|", 0, "5-Digit Zip|", {{"Black", "Sum", "Black", }}, null)

 

Error Codes

Error Type	Meaning
Error	The aggregation method or other inputs are invalid
NotFound	A layer name, set name, or field name is invalid

 

See Also

Function	Summary
AggregateTable()	Groups records in a view and computes summary statistics
ApplyOverlayTable()	Computes attribute values for a view using information from an overlay table
ComputeIntersectionPercentages()	In Intersects two or more area or line layers and computes the intersection percentages