Coyote Graphics Routines

Date: Fri Mar 27 12:14:20 2015

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result = cgSetIntersection(set_a, set_b [, COUNT=integer] [, INDICES_A=integer] [, INDICES_B=integer] [, NORESULT=NORESULT] [, POSITIONS=integer] [, /SUCCESS])

This function is used to find the intersection between two sets of integers.

Return value

A vector of values that are found in both set_a and set_b.


set_a in required type=integer

A vector of integers.

set_b in required type=integer

A vector of integers.


COUNT out optional type=integer

This keyword contains the number of elements in the intersection vector.

INDICES_A out optional type=integer

The indices in vector A where the intersected values appear. Note, this requires the intersected points be unique in each vector. The Positions keyword will return ALL the positions of the match, even if there are non-unique matches.

INDICES_B out optional type=integer

The indices in vector B where the intersected values appear. This assumes that the intersected points are represented uniquely in the A and B vectors.

NORESULT in optional

Set this keyword to a value that will be returned from the function if no intersection between the two sets of numbers is found. By default, -1.

POSITIONS out optional type=integer

This keyword returns the positions or locations in A where the values in B appear.

SUCCESS out optional type=boolean

This keyword is set to 1 if an intersection was found, and to 0 otherwise.


Here is how to use this program:

IDL> set_a = [1,2,3,4,5] IDL> set_b = [4,5,6,7,8,9,10,11] IDL> Print, cgSetIntersection(set_a, set_b) 4 5
See for other types of set operations.

Author information



David W. Fanning 1645 Sheely Drive Fort Collins, CO 80526 USA Phone: 970-221-0438 E-mail: Coyote's Guide to IDL Programming:


Copyright (c) 2009-2013, Fanning Software Consulting, Inc.


Change History:

Written by: David W. Fanning, October 31, 2009, from code originally supplied to the IDL newsgroup by Research Systems software engineers. Yikes, bug in original code only allowed positive integers. Fixed now. 2 Nov 2009. DWF. Fixed a problem when one or both of the sets was a scalar value. 18 Nov 2009. DWF. Added a POSITIONS keyword. 30 Nov 2012. DWF. Added a COUNT keyword 3 Dec 2012. DWF. Added INDICES_A and INDICES_B keywords at R.G. Stockwell's suggestion. 13 Dec 2012. DWF.

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