ComputeIntersectionPercentages()

Summary

Intersects two or more area or line layers and computes the intersection percentages.

 

Syntax

ComputeIntersectionPercentages(array layer_sets, string table, array options)

 

Argument	Contents
layer_sets	The layer and/or set names of area or line features to intersect
table	The filename of the table to create; the file extension must be one of .BIN, .CSV, .DBF, or .TXT

 

Option	Type	Contents
Database	String	The path and file name for the resulting geographic database; or null if you do not want to produce a geographic file
Label	String	A descriptive label for the geographic file
Layer Name	String	The name of the layer in the geographic file
Optimize	Boolean	If "True" (default), and the Database option is specified, the database will be optimized, otherwise "False"

 

Notes

• For areas, ComputeIntersectionPercentages() takes two or more area layers and/or sets and intersects all the boundary edges to create a new area database. For each resulting area, the data table contains a record with the original feature ID from each layer and the percentage of the original area size for each layer.

• For lines, ComputeIntersectionPercentages() takes two or more line layers and/or sets and intersects all the lines to create a new line database. For each resulting line, the data table contains a record with the original feature ID and a percent of 1 for the source layer and either:

• • A null value for the ID and a percent of 0 for the other layer(s), or

  • Where they overlap the ID of the line with which it overlaps and a percent of 1.

• You cannot mix layer types. They must all be either area layers or line layers. The layer type is determined from the input layers.

• ComputeIntersectionPercentages() can also operate on a single layer, for example finding where the lines of a line layer intersect each other or themselves.

• ComputeIntersectionPercentages() displays a progress bar. To add a Cancel button to the progress bar, precede the function call with an "on escape" clause. For more information, see Error Handling.

• The total number of areas that can be intersected is limited by the amount of available memory.

Example

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

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

folder = RunMacro("G30 Tutorial Folder")

ComputeIntersectionPercentages({"Tract", "5-Digit Zip"}, folder+"myintersect.dbf",

{{"Database", folder + "myoverlay.dbd"}, {"Optimize", "False"}}) 

// Open myintersect.dbf and myoverlay.dbd in the Tutorial folder

// to see the results.

 

Error Codes

Error	Meaning
NotFound	One or more of the layer or sets does not exist
Error	An argument or option has the wrong type or the wrong number of values; or an error occurred while processing the data; or no layer or sets are specified; or they are specified incorrectly.
Escape	The user clicked Cancel

 

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
ColumnAggregate()	Performs a geographic overlay between two layers and aggregates tabular data
MergeByValue()	Creates districts by merging areas from a geographic file, based on the value of a field
MergeGeography()	Merges features from one layer into another
SelfAggregate()	Groups the records in a view, based on a field, to create an aggregate view