;+ ; NAME: ; SETDIFFERENCE ; ; PURPOSE: ; ; This function is used to find the difference between two sets of integers. ; In other words, the function will find the values that are in Set A but ; are missing in Set B. ; ; AUTHOR: ; ; FANNING SOFTWARE CONSULTING ; David Fanning, Ph.D. ; 1645 Sheely Drive ; Fort Collins, CO 80526 USA ; Phone: 970-221-0438 ; E-mail: david@idlcoyote.com ; Coyote's Guide to IDL Programming: http://www.idlcoyote.com/ ; ; CATEGORY: ; ; Utilities ; ; CALLING SEQUENCE: ; ; difference = SetDifference(set_a, set_b) ; ; RETURN VALUE: ; ; difference: A vector of values that are found in set_a but are missing in set_b. ; ; ARGUMENTS: ; ; set_a: A vector of integers. ; ; set_b: A vector of integers. ; ; KEYWORDRS: ; ; COUNT: An output variable that contains the number of elements in the difference vector. ; ; NORESULT: Set this keyword to a value that will be returned from the function ; if no difference between the two sets of numbers is found. By default, set_a. ; ; POSITIONS: An output keyword that will return the positions or locations in A of the values ; not found in B. ; ; SUCCESS: An output keyword that is set to 1 if a difference was found, and to 0 otherwise. ; ; EXAMPLE: ; ; IDL> set_a = [1,2,3,4,5] ; IDL> set_b = [4,5,6,7,8,9,10,11] ; IDL> Print, SetDifference(set_a, set_b) ; 1 2 3 ; ; See http://www.idlcoyote.com/tips/set_operations.html for other types of set operations. ; ; NOTES: ; ; If you read the Set Operations article pointed to above, you will see quite a lot of ; discussion about what kinds of algorithms are faster than others. The Histogram ; algorithms implemented here are sometimes NOT the fastest algorithms, especially ; for sparse arrays. If this is a concern in your application, please be sure to read ; that article. ; ; MODIFICATION HISTORY: ; ; Written by: David W. Fanning, November 25, 2009, from code originally supplied to the IDL ; newsgroup by Research Systems software engineers. ; Added COUNT and POSITIONS keywords. Liam Steele, 13 Dec 2012. ; Defined values for COUNT and POSITIONS when there is no overlap in the vectors. 14 Dec 2012. LS. ;- ;******************************************************************************************; ; Copyright (c) 2009, by Fanning Software Consulting, Inc. ; ; All rights reserved. ; ; ; ; Redistribution and use in source and binary forms, with or without ; ; modification, are permitted provided that the following conditions are met: ; ; ; ; * Redistributions of source code must retain the above copyright ; ; notice, this list of conditions and the following disclaimer. ; ; * Redistributions in binary form must reproduce the above copyright ; ; notice, this list of conditions and the following disclaimer in the ; ; documentation and/or other materials provided with the distribution. ; ; * Neither the name of Fanning Software Consulting, Inc. nor the names of its ; ; contributors may be used to endorse or promote products derived from this ; ; software without specific prior written permission. ; ; ; ; THIS SOFTWARE IS PROVIDED BY FANNING SOFTWARE CONSULTING, INC. ''AS IS'' AND ANY ; ; EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES ; ; OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT ; ; SHALL FANNING SOFTWARE CONSULTING, INC. BE LIABLE FOR ANY DIRECT, INDIRECT, ; ; INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED ; ; TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; ; ; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ; ; ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT ; ; (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS ; ; SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. ; ;******************************************************************************************; FUNCTION SetDifference, set_a, set_b, $ COUNT=count, $ NORESULT=noresult, $ POSITIONS=positions, $ SUCCESS=success Compile_Opt StrictArr, DefInt32 ; Set up noresult value. IF N_Elements(noresult) EQ 0 THEN noresult = set_a ; Error handling. Catch, theError IF theError NE 0 THEN BEGIN Catch, /CANCEL void = Error_Message() success = 0 RETURN, noresult ENDIF ; Check parameters. IF N_Params() NE 2 THEN Message, 'Two input parameters or sets are required.' ; The input sets must be integers. IF (Size(set_a, /TYPE) GT 3) AND (Size(set_a, /TYPE) LT 12) THEN $ Message, 'Set A must be an integer array.' IF (Size(set_b, /TYPE) GT 3) AND (Size(set_b, /TYPE) LT 12) THEN $ Message, 'Set B must be an integer array.' ; If either of the sets is a scalar, make it a vector. IF N_Elements(set_a) EQ 1 && (Size(set_a))[0] EQ 0 THEN set_a = [set_a] IF N_Elements(set_b) EQ 1 && (Size(set_b))[0] EQ 0 THEN set_b = [set_b] ; Assume success. success = 1 count = 0 ; Find the set ranges. mina = Min(set_a, Max=maxa) minb = Min(set_b, Max=maxb) ; If no overlap, return no result. IF (minb GT maxa) OR (maxb LT mina) THEN BEGIN success = 0 count = N_Elements(set_a) positions = Lindgen(count) RETURN, noresult ENDIF ; Otherwise find the indices in A that are not in B. r = Where((Histogram(set_a, Min=mina, Max=maxa, REVERSE_INDICES=ra) NE 0) AND $ ( Histogram(set_b, Min=mina, Max=maxa) EQ 0), count) ; Do you want the positions in A not found in B? IF Arg_Present(positions) THEN BEGIN FOR j=0,N_Elements(r)-1 DO BEGIN IF N_Elements(thesePositions) EQ 0 THEN BEGIN thesePositions = [ReverseIndices(ra, r[j])] ENDIF ELSE BEGIN thesePositions = [thesePositions, ReverseIndices(ra, r[j])] ENDELSE ENDFOR positions = thesePositions ENDIF ; Return the result. IF count EQ 0 THEN BEGIN success = 0 RETURN, noresult ENDIF ELSE RETURN, r + mina END