Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / signal-1.1.3 / convmtx.m

diff --git a/octave_packages/signal-1.1.3/convmtx.m b/octave_packages/signal-1.1.3/convmtx.m
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+## Copyright (C) 2003 David Bateman <adb014@gmail.com>
+##
+## This program 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 3 of the License, or (at your option) any later
+## version.
+##
+## This program 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
+## this program; if not, see <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {} convmtx (@var{a}, @var{n})
+## If @var{a} is a column vector and @var{x} is a column vector
+## of length @var{n}, then 
+##
+## @code{convmtx(@var{a}, @var{n}) * @var{x}}
+##
+## gives the convolution of of @var{a} and @var{x} and is the
+## same as @code{conv(@var{a}, @var{x})}. The difference is if
+## many vectors are to be convolved with the same vector, then
+## this technique is possibly faster.
+##
+## Similarly, if @var{a} is a row vector and @var{x} is a row 
+## vector of length @var{n}, then
+##
+## @code{@var{x} * convmtx(@var{a}, @var{n})}
+##
+## is the same as @code{conv(@var{x}, @var{a})}.
+## @end deftypefn
+## @seealso{conv}
+
+function b = convmtx (a, n)
+
+  if (nargin != 2)
+    print_usage;
+  endif
+   
+  [r, c] = size(a);
+  
+  if ((r != 1) && (c != 1)) || (r*c == 0)
+    error("convmtx: expecting vector argument");
+  endif
+  
+  b = toeplitz([a(:); zeros(n-1,1)],[a(1); zeros(n-1,1)]);
+  if (c > r)
+    b = b.';
+  endif
+
+endfunction
+
+%!assert(convmtx([3,4,5],3),[3,4,5,0,0;0,3,4,5,0;0,0,3,4,5])
+%!assert(convmtx([3;4;5],3),[3,0,0;4,3,0;5,4,3;0,5,4;0,0,5])