dot.m

JAVA 数学程序库 提供常规的数值计算程序包

## Copyright (C) 1998 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, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
## 02110-1301, USA.

## -*- texinfo -*-
## @deftypefn {Function File} {} dot (@var{x}, @var{y}, @var{dim})
## Computes the dot product of two vectors. If @var{x} and @var{y}
## are matrices, calculate the dot-product along the first 
## non-singleton dimension. If the optional argument @var{dim} is
## given, calculate the dot-product along this dimension.
## @end deftypefn

## Author: jwe

function z = dot (x, y, dim)

  if (nargin != 2 && nargin != 3)
    print_usage ();
  endif

  if (nargin < 3)
    if (isvector (x))
      x = x(:);
    endif
    if (isvector (y))
      y = y(:);
    endif
    if (! size_equal (x, y))
      error ("dot: sizes of arguments must match")
    endif
    z = sum(x .* y);
  else
    if (! size_equal (x, y))
      error ("dot: sizes of arguments must match")
    endif
    z = sum(x .* y, dim);
  endif

endfunction

/*
@GROUP
LinearAlgebra
@SYNTAX
dot()
@DOC
.
@EXAMPLES
<programlisting>
</programlisting>
@NOTES
@SEE
*/