## Copyright (C) 2003 David Bateman ## ## 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 2 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) usage ("convmtx (a, n)"); 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])

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