From octave-sources-request at bevo dot che dot wisc dot edu  Thu Oct  5 16:01:22 2000
Subject: outer.m (again)
From: Paul Kienzle <pkienzle at kienzle dot powernet dot co dot uk>
To: octave-sources at bevo dot che dot wisc dot edu
Cc: mathyant at student dot ethz dot ch
Date: Thu, 05 Oct 2000 11:56:06 +0100


A further x3 speedup for outer(x,y) by using * rather than .*

## Copyright (C) 2000 Antoine Mathys
##
## 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{a} =} outer (@var{x}, @var{y}, [@var{f}])
## Given two vectors of length  at var{m} and @var{n}, return a
##  at var{m}-by-@var{n} matrix with entries @var{f (x(i), y(j))}.
##
## If  at var{f} is omitted, multiplication is the default.
##
##  at deftypefnx {Function File} {@var{a} =} outer (@var{x}, @var{y}, @var{f}, 'matrix')
## Pass matrices to function  at var{f} instead of individual elements.
##  at end deftypefn

## Author: Antoine Mathys <mathyant at student dot ethz dot ch>
## Created: 2 October 2000
## Adapted-By: Antoine Mathys

function retval = outer (x, y, f, matrix)

  if (nargin < 2 || nargin > 4)
    usage ("outer (x, y [, f [, 'matrix']])");
  endif
  
  if (!is_vector(x) || !is_vector(y))
    error ("outer: both x and y must be vectors");
  endif

  m = length (x);
  n = length (y);

  if nargin == 2
    retval = x(:) * y(:).';
  elseif nargin == 4
    x = x (:);
    x = x (:, ones (1, n));
    y = y (:).';
    y = y (ones (1, m), :);
    retval = feval (f, x, y);
  else
    retval = zeros (m, n);
    for i=1:m
      for j=1:n
	retval (i, j) = feval (f, x(i), y(j));
      endfor
    endfor
  endif

endfunction



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