ApplyOverlayTable()

Summary

Computes attribute values for a view using information from an overlay table.

 

Syntax

rslt = ApplyOverlayTable(string new_view, string overlay_table_filename, string input_view, string output_type, string output_filename, array output_fields, array options)

 

Argument	Contents
new_view	The desired name for the result view
overlay_table_filename	The filename of an overlay table
input_view_name	The name of the input view
output_type	The type of file to create ("CSV", "dBASE", "FFA" or "FFB")
output_filename	The name of the output file
output_fields	An array containing one element for each field in the output table. Each element is an array of three items, that indicates the statistic calculated, as shown below

 

Item	Type	Contents
1	String	Name of a field in the input view
2	String	Statistic: "SUM", "MIN", "MAX", 'DOM" (DOMINANT), "AVG" (AVERAGE), "STDDEV" or "COUNT"
3 (optional)	String	Name of a field in the input view used in computing averages. Necessary only for averages; must be a numeric field

 

Option	Type	Contents
Missing as zero	N/A	No contents necessary. This option causes all missing numeric values in the input view to be treated as zeros in sum, average, min or max calculations

 

Returns

A string containing the name of the view of the new table.

 

Notes

• The file types include FFA for fixed-format text (ASCII), FFB for fixed-format binary, and CSV for comma-separated text (values).

• ApplyOverlayTable() computes attribute values for features in a layer, based on an overlay table that indicates the level of intersection between features in the current layer and features in another layer. The results are written to a new table file, and the table is opened to create a view. The overlay table must be the result of a geographic overlay operation between two area layers (see ComputeIntersectionPercentages()).

• For numeric fields, you must use the sum, min, max, or average statistic. By default, any missing numeric values in the input view result in a missing value.

• For string-type input data fields, only the dominant mode is supported. The dominant mode chooses the value from the largest intersecting record.

• The average statistic calculates weighted averages, and requires a weighting field (this is the optional third field listed above).

• The output table has one record for each record in the first layer used to create the overlay table.

• The output table has one column containing the record ID, plus one column for each statistic requested in output_fields.

• The output_fields array cannot be null.

• The name, width and number of decimals for all output fields are automatically determined. The name is determined as follows:

Statistic	Prefix	Example
Sum	(none)	Income
Min	Low	Low Income
Max	High	High Income
Average	Avg	Avg Income

 

Example

// Before running this example, run the ComputeIntersectionPercentages() example,

// and then make sure to create a map by opening manh_zip.cdf in the

// Tutorial folder
folder = RunMacro("G30 Tutorial Folder")

rslt = ApplyOverlayTable("New Overlay Table", folder + "myintersect.dbf",

"5-Digit Zip", "FFB", "folder + "aggtable.bin", { {"White", "Sum", }, {"Population", "Sum", }, {"Population", "Avg", } }, ) 

 

Error Codes

Error Type	Meaning
Error	The output_fields array does not have the correct format; one or more of the following input variables is null or invalid: new_view, overlay_table_filename, output_type, output_filename, output_fields; the overlay table is not valid; input_view_name does not correspond to a mappable view; or a file I/O error occurred (e.g., out of disk space)
NotFound	The input view does not exist, the input overlay table does not exist, or one of the data fields does not exist

 

See Also

Function	Summary
AggregateTable()	Groups records in a view and computes summary statistics
ComputeIntersectionPercentages()	Intersects two or more area or line layers and computes the intersection percentages
AggregateTable()	Groups records in a view and computes summary statistics
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
SelfAggregate()	Groups the records in a view, based on a field, to create an aggregate view