reverseindices.pro
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; docformat = 'rst'
;
; NAME:
; ReverseIndices
;
; PURPOSE:
; Provides a simple way to obtain the data indices from a Histogram REVERSE_INDICES
; vector. Returns a -1 if no indices are available. Check the COUNT keyword for the
; number of indices returned.
;
;******************************************************************************************;
; ;
; Copyright (c) 2011, 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. ;
;******************************************************************************************;
;
;+
; :Description:
; Provides a simple way to obtain the data indices from a Histogram REVERSE_INDICES
; vector. Returns a -1 if no indices are available. Check the COUNT keyword for the
; number of indices returned.
;
; :Categories:
; Utilities
;
; :Params:
; reverse_indices: in, required, type=integer
; The REVERSE_INDICES vector that is returned from the HISTOGRAM command.
; index: in, required, type=integer
; The zero-based index into the REVERSE_INDICES vector from which to obtain
; the indices. For example, and index value of 4 will return the indices in
; the 5th bin (zero based counting) of the histogram.
;
; :Keywords:
; count: out, optional, type=Long
; The number of indices returned by the function.
;
; :Return Value:
; indices:
; The indices that were put into the indexth bin of the histogram. A -1
; is returned if no indices are in that particular bin.
;
; :Examples:
; Used with the HISTOGRAM command::
; IDL> image = cgDemoData(7)
; IDL> h = Histogram(image, REVERSE_INDICES=ri)
; IDL> indices = ReverseIndices(ri, 4, COUNT=cnt)
; IDL> Help, indices, cnt, h[4]
; INDICES LONG = Array[948]
; CNT LONG = 948
; <Expression> LONG = 948
; IDL> image[indices] = 0
;
; :Author:
; FANNING SOFTWARE CONSULTING::
; David W. Fanning
; 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
;
; :History:
; Written by David W. Fanning at suggestion of Ben Tupper. 7 January 2011.
;
; :Copyright:
; Copyright (c) 2011, Fanning Software Consulting, Inc.
;-
FUNCTION ReverseIndices, ri, index, COUNT=count
Compile_Opt idl2
; Error handling.
Catch, theError
IF theError NE 0 THEN BEGIN
Catch, /CANCEL
void = Error_Message()
count = 0
RETURN, -1
ENDIF
; Need two parameters.
IF N_Params() NE 2 THEN Message, 'Two positional parameters, REVERSE_INDICES and INDEX, are required.'
; Return the indices, if there are any.
IF ri[index] NE ri[index+1] THEN BEGIN
indices = ri[ri[index]:ri[index+1]-1]
count = N_Elements(indices)
ENDIF ELSE BEGIN
indices = -1
count = 0
ENDELSE
RETURN, indices
END