1 ## Copyright (C) 1994-2012 John W. Eaton
3 ## This file is part of Octave.
5 ## Octave is free software; you can redistribute it and/or modify it
6 ## under the terms of the GNU General Public License as published by
7 ## the Free Software Foundation; either version 3 of the License, or (at
8 ## your option) any later version.
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12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 ## General Public License for more details.
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17 ## <http://www.gnu.org/licenses/>.
20 ## @deftypefn {Function File} {} conv (@var{a}, @var{b})
21 ## @deftypefnx {Function File} {} conv (@var{a}, @var{b}, @var{shape})
22 ## Convolve two vectors @var{a} and @var{b}.
24 ## The output convolution is a vector with length equal to
25 ## @code{length (@var{a}) + length (@var{b}) - 1}.
26 ## When @var{a} and @var{b} are the coefficient vectors of two polynomials, the
27 ## convolution represents the coefficient vector of the product polynomial.
29 ## The optional @var{shape} argument may be
32 ## @item @var{shape} = "full"
33 ## Return the full convolution. (default)
35 ## @item @var{shape} = "same"
36 ## Return the central part of the convolution with the same size as @var{a}.
39 ## @seealso{deconv, conv2, convn, fftconv}
42 ## Author: Tony Richardson <arichard@stark.cc.oh.us>
46 function y = conv (a, b, shape = "full")
48 if (nargin < 2 || nargin > 3)
52 if (! (isvector (a) && isvector (b)))
53 error ("conv: both arguments A and B must be vectors");
54 elseif (nargin == 3 && ! any (strcmpi (shape, {"full", "same"})))
55 error ('conv: SHAPE argument must be "full" or "same"');
68 ## Use shortest vector as the coefficent vector to filter.
70 [a, b] = deal (b, a); # Swap vectors
75 ## Pad longer vector to convolution length.
77 x(end+1:end+ly-lb) = 0;
82 if (strcmp (shape, "same"))
83 idx = ceil ((ly - la) / 2);
95 %! assert (conv (x, x), [1; 2; 3; 2; 1]);
96 %! assert (conv (y, y), [1, 2, 3, 2, 1]);
97 %! assert (conv (x, y), [1, 2, 3, 2, 1]);
98 %! assert (conv (y, x), [1; 2; 3; 2; 1]);
99 %! assert (conv (c, x), [3; 3; 3]);
100 %! assert (conv (c, y), [3, 3, 3]);
101 %! assert (conv (x, c), [3; 3; 3]);
102 %! assert (conv (y, c), [3, 3, 3]);
103 %! assert (conv (b, c), 6);
108 %! assert (size (conv(a,b)), [1, numel(a)+numel(b)-1]);
109 %! assert (size (conv(b,a)), [1, numel(a)+numel(b)-1]);
114 %! assert (size (conv(a,b)), [numel(a)+numel(b)-1, 1]);
115 %! assert (size (conv(b,a)), [numel(a)+numel(b)-1, 1]);
120 %! assert (size (conv(a,b)), [1, numel(a)+numel(b)-1]);
121 %! assert (size (conv(b,a)), [1, numel(a)+numel(b)-1]);
126 %! assert (conv (a,b,"full"), conv (a,b));
127 %! assert (conv (b,a,"full"), conv (b,a));
132 %! assert (conv (a,b,"same"), [4, 10, 16, 22, 28, 34, 40, 46, 52, 47]);
133 %! assert (conv (b,a,"same"), [28, 34, 40]);
135 %% Test input validation
137 %!error conv (1,2,3,4)
138 %!error conv ([1, 2; 3, 4], 3)
139 %!error conv (3, [1, 2; 3, 4])
140 %!error conv (2, 3, "XXXX")