# Copyright (C) 1996 Auburn University.  All Rights Reserved.
#
# This file is part of Octave. 
#
# Octave is free software; you can redistribute it and/or modify it 
# under the terms of the GNU General Public License as published by the 
# Free Software Foundation; either version 2, or (at your option) any 
# later version. 
# 
# Octave is distributed in the hope that it will be useful, but WITHOUT 
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 
# FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License 
# for more details.
# 
# You should have received a copy of the GNU General Public License 
# along with Octave; see the file COPYING.  If not, write to the Free 
# Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. 
 
function [yy,idx] = sortcom(xx,opt)
# [yy,idx] = sortcom(xx[,opt]): sort a complex vector
# xx: complex vector
# opt: sorting option:
#	"re": real part (default)
#	"mag": by magnitude
#	"im": by imaginary part
#
#  if opt != "im" then values with common real part/magnitude are
#     sorted by imaginary part, i.e. a - jb followed by a + jb. 
#     [Complex conjugate pairs may not be grouped consecutively if more than 2
#     numbers share a common real part/magnitude]
# yy: sorted values
# idx: permutation vector: yy = xx(idx)

# Written by A. S. Hodel June 1995

  if( nargin < 1 | nargin > 2 )
     usage("yy = sortcom(xx[,opt]");
  elseif( !(is_vector(xx) | isempty(xx) ))
    error("sortcom: first argument must be a vector");
  endif

  if(nargin == 1)         opt = "re";
  else
    if (!isstr(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: illegal 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