## Copyright (C) 1996, 2000, 2002, 2004, 2005, 2006, 2007
##               Auburn University.  All rights reserved.
##
## This file is part of Octave.
##
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## under the terms of the GNU General Public License as published by
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## -*- texinfo -*-
## @deftypefn {Function File} {[@var{yy}, @var{idx}] =} sortcom (@var{xx}[, @var{opt}])
## Sort a complex vector.
##
## @strong{Inputs}
## @table @var
## @item xx
## Complex vector
## @item opt
## sorting option:
## @table @code
## @item "re"
## Real part (default);
## @item "mag"
## By magnitude;
## @item "im"
## By imaginary part.
## @end table
## if @var{opt} is not chosen as @code{"im"}, then complex conjugate pairs are grouped together,
## @math{a - jb} followed by @math{a + jb}.
## @end table
##
## @strong{Outputs}
## @table @var
## @item yy
## Sorted values
## @item idx
## Permutation vector: @code{yy = xx(idx)}
## @end table
## @end deftypefn

## Author: A. S. Hodel <a.s.hodel@eng.auburn.edu>
## Created: June 1995

function [yy, idx] = sortcom (xx, opt)

  if( nargin < 1 | nargin > 2 )
     print_usage ();
  elseif( !(isvector(xx) | isempty(xx) ))
    error("sortcom: first argument must be a vector");
  endif

  if(nargin == 1)         opt = "re";
  else
    if (!ischar(opt))
      error("sortcom: second argument must be a string");
    endif
  endif

  if(isempty(xx))
    yy = idx = [];
  else
    if(strcmp(opt,"re"))        datavec = real(xx);
    elseif(strcmp(opt,"im"))    datavec = imag(xx);
    elseif(strcmp(opt,"mag"))   datavec = abs(xx);
    else                        error(["sortcom: invalid option = ", opt])
    endif

    [datavec,idx] = sort(datavec);
    yy= xx(idx);

    if(strcmp(opt,"re") | strcmp(opt,"mag"))
      ## sort so that complex conjugate pairs appear together

      ddiff = diff(datavec);
      zidx = find(ddiff == 0);

      ## sort common datavec values
      if(!isempty(zidx))
        for iv=create_set(datavec(zidx))
          vidx = find(datavec == iv);
          [vals,imidx] = sort(imag(yy(vidx)));
          yy(vidx)  = yy(vidx(imidx));
          idx(vidx) = idx(vidx(imidx));
        endfor
      endif
    endif
  endif
endfunction