File: cgscalevector.pro

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; docformat = 'rst'
;
; NAME:
;   cgScaleVector
;
; PURPOSE:
;   This is a utility routine to scale the elements of a vector or an array into a 
;   given data range. 
;
;******************************************************************************************;
;                                                                                          ;
;  Copyright (c) 1998-2013, 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.                            ;
;******************************************************************************************;
;
;+
; This is a utility routine to scale the elements of a vector or an array into a 
; given data range. 
;
; :Categories:
;    Utilities
;    
; :Returns:
;     A vector or array of the same size as the input, scaled into the data range given
;     by `minRange` and `maxRange'. The input vector is confined to the data range set
;     by `MinValue` and `MaxValue` before scaling occurs.
;
; :Params:
;    maxRange: in, optional, type=varies, default=1
;       The maximum output value of the scaled vector. Set to 1 by default.
;    minRange: in, optional, type=varies, default=0
;       The minimum output value of the scaled vector. Set to 0 by default.
;    vector: in, required
;       The input vector or array to be scaled.
;
; :Keywords:
;    double: in, optional, type=boolean, default=0
;       Set this keyword to perform scaling in double precision. Otherwise, scaling 
;       is done in floating point precision.
;    maxvalue: in, optional
;       Set this value to the maximum value of the vector, before scaling (vector < maxvalue).
;       The default value is Max(vector).
;    minvalue: in, optional
;       Set this value to the mimimum value of the vector, before scaling (minvalue < vector).
;       The default value is Min(vector).
;    nan: in, optional, type=boolean, default=0
;       Set this keyword to enable not-a-number checking. NANs in vector will be ignored.
;    preserve_type: in, optional, type=boolean, default=0
;       Set this keyword to preserve the input data type in the output.
;
; :Examples:
;       Simple example of scaling a vector::
;       
;          IDL> x = [3, 5, 0, 10]
;          IDL> xscaled = cgScaleVector(x, -50, 50)
;          IDL> Print, xscaled
;               -20.0000     0.000000     -50.0000      50.0000

;       Suppose your image has a minimum value of -1.7 and a maximum value = 2.5.
;       You wish to scale this data into the range 0 to 255, but you want to use
;       a diverging color table. Thus, you want to make sure value 0.0 is scaled to 128.
;       You proceed like this::
;
;          scaledImage = cgScaleVector(image, 0, 255, MINVALUE=-2.5, MAXVALUE=2.5)
;
; :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:
;     Change History::
;         Written by:  David W. Fanning, 12 Dec 1998.
;         Added MAXVALUE and MINVALUE keywords. 5 Dec 1999. DWF.
;         Added NAN keyword. 18 Sept 2000. DWF.
;         Removed check that made minRange less than maxRange to allow ranges to be
;            reversed on axes, etc. 28 Dec 2003. DWF.
;         Added PRESERVE_TYPE and DOUBLE keywords. 19 February 2006. DWF.
;         Added FPUFIX to cut down on floating underflow errors. 11 March 2006. DWF.
;         Renamed Scale_Vector to cgScaleVector, 16 May 2013. DWF.
;
; :Copyright:
;     Copyright (c) 1998-2013, Fanning Software Consulting, Inc.
;-
FUNCTION cgScaleVector, vector, minRange, maxRange, $
   DOUBLE=double, $
   MAXVALUE=vectorMax, $
   MINVALUE=vectorMin, $
   NAN=nan, $
   PRESERVE_TYPE=preserve_type

   ; Error handling.
   Catch, theError
   IF theError NE 0 THEN BEGIN
      Catch, /Cancel
      void = cgErrorMsg()
      RETURN, vector
   ENDIF

   ; Check positional parameters.
   CASE N_Params() OF
      0: Message, 'Incorrect number of arguments.'
      1: BEGIN
         IF Keyword_Set(double) THEN BEGIN
            minRange = 0.0D
            maxRange = 1.0D
         ENDIF ELSE BEGIN
            minRange = 0.0
            maxRange = 1.0
         ENDELSE
         ENDCASE
      2: BEGIN
         IF Keyword_Set(double) THEN maxRange = 1.0D > (minRange + 0.0001D) ELSE $
            maxRange = 1.0 > (minRange + 0.0001)
         ENDCASE
      ELSE:
   ENDCASE

   ; If input data type is DOUBLE and DOUBLE keyword is not set, then set it.
   IF Size(FPUFIX(vector), /TNAME) EQ 'DOUBLE' AND N_Elements(double) EQ 0 THEN double = 1

   ; Make sure we are working with at least floating point numbers.
   IF Keyword_Set(double) THEN minRange = DOUBLE( minRange ) ELSE minRange = FLOAT( minRange )
   IF Keyword_Set(double) THEN maxRange = DOUBLE( maxRange ) ELSE maxRange = FLOAT( maxRange )

   ; Make sure we have a valid range.
   IF maxRange EQ minRange THEN Message, 'Range max and min are coincidental'

   ; Check keyword parameters.
   IF Keyword_Set(double) THEN BEGIN
      IF N_Elements(vectorMin) EQ 0 THEN vectorMin = Double( Min(FPUFIX(vector), NAN=1) ) $
         ELSE vectorMin = Double(vectorMin)
      IF N_Elements(vectorMax) EQ 0 THEN vectorMax = DOUBLE( Max(FPUFIX(vector), NAN=1) ) $
         ELSE vectorMax = DOUBLE( vectorMax )
   ENDIF ELSE BEGIN
      IF N_Elements(vectorMin) EQ 0 THEN vectorMin = FLOAT( Min(FPUFIX(vector), NAN=1) ) $
         ELSE vectorMin = FLOAT( vectorMin )
      IF N_Elements(vectorMax) EQ 0 THEN vectorMax = FLOAT( Max(FPUFIX(vector), NAN=Keyword_Set(nan)) ) $
         ELSE vectorMax = FLOAT( vectorMax )
   ENDELSE

   ; Trim vector before scaling.
   index = Where(Finite(vector) EQ 1, count)
   IF count NE 0 THEN BEGIN
      IF Keyword_Set(double) THEN trimVector = Double(vector) ELSE trimVector = Float(vector)
      trimVector[index]  =  vectorMin >  vector[index] < vectorMax
   ENDIF ELSE BEGIN
      IF Keyword_Set(double) THEN trimVector = vectorMin > Double(vector) < vectorMax ELSE $
         trimVector = vectorMin > Float(vector) < vectorMax
   ENDELSE

   ; Calculate the scaling factors.
   scaleFactor = [((minRange * vectorMax)-(maxRange * vectorMin)) / $
       (vectorMax - vectorMin), (maxRange - minRange) / (vectorMax - vectorMin)]

   ; Clear math errors.
   void = Check_Math()

   ; Return the scaled vector.
   IF Keyword_Set(preserve_type) THEN BEGIN
      RETURN, FPUFIX(Convert_To_Type(trimVector * scaleFactor[1] + scaleFactor[0], Size(vector, /TNAME)))
   ENDIF ELSE BEGIN
      RETURN, FPUFIX(trimVector * scaleFactor[1] + scaleFactor[0])
   ENDELSE

END