From bug-octave-request at bevo dot che dot wisc dot edu  Tue Aug  1 11:00:53 2000
Subject: mesh*.m complex argument vectors
From: Rolf Fabian <fabian at tu-cottbus dot de>
To: "'bug-octave UWISC'" <bug-octave at bevo dot che dot wisc dot edu>
Date: Tue, 1 Aug 2000 11:01:36 -0500 (CDT)

Hi,

The help part of 'scripts/plot/meshgrid.m' says:
  ## The rows of  at var{xx} are copies of @var{x},
  ## and the columns of  at var{yy} are copies of @var{y}.
Depending on orientation, this is incorrect if complex
x,y vectors are involved, namely if x is column type, 
or/and y is row type. Then erraneously complex conjugated
copies are returned!

e.g.
:> [X,Y]=meshgrid([i;2i],[3i,4i])
X =
  0 - 1i  0 - 2i
  0 - 1i  0 - 2i
Y =
  0 - 3i  0 - 3i
  0 - 4i  0 - 4i

( I've no idea what Matlab does in this case )

Note, that analogous incorrect features appears in all mesh*.m scripts,
i.e. also in 'meshdom.m' and 'mesh.m'.

Rolf Fabian


simple correction for e.g. 'meshgrid.m' ( see lines *FIXED* )
---- snip --- snip -- snip -- snip ---

## Copyright (C) 1996, 1997 John W. Eaton
##
## 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, 59 Temple Place - Suite 330, Boston, MA
## 02111-1307, USA.

## -*- texinfo -*-
##  at deftypefn {Function File} {[@var{xx}, @var{yy}] =} meshgrid (@var{x}, @var{y})
##  at deftypefnx {Function File} {[@var{xx}, @var{yy}] =} meshgrid (@var{x})
## Given vectors of  at var{x} and @var{y} coordinates, return two matrices corresponding
## to the  at var{x} and @var{y} coordinates of a mesh.  The rows of @var{xx} are copies of @var{x},
## and the columns of  at var{yy} are copies of @var{y}.
##  at end deftypefn
##  at seealso{sombrero, plot, semilogx, semilogy, loglog, polar, mesh, meshdom, contour,
## bar, stairs, gplot, gsplot, replot, xlabel, ylabel, and title}

## Author: jwe

function [xx, yy] = meshgrid (x, y)

  if (nargin == 1)
    y = x;
  endif
  if (nargin > 0 && nargin < 3)
    if (is_vector (x) && is_vector (y))
      xlen = length (x);
      ylen = length (y);
      xx = zeros (ylen, xlen);
      yy = zeros (ylen, xlen);
      if (columns (x) == 1)
        #x = x';			#original 2.1.31
         x = x.';			#*FIXED*
      endif
      if (rows (y) == 1)
        #y = y';			#original 2.1.31
         y = y.';			#*FIXED*
      endif
      for i = 1:ylen
        xx(i,:) = x;
      endfor
      for i = 1:xlen
        yy(:,i) = y;
      endfor
    else
      error ("meshgrid: arguments must be vectors");
    endif
  else
    usage ("[xx, yy] = meshgrid (x, y)");
  endif

endfunction
---- snip --- snip -- snip -- snip --



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