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annotate scripts/signal/fftconv.m @ 1026:9fc405c8c06c

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[project @ 1995-01-11 21:17:01 by jwe]
author jwe
date Wed, 11 Jan 1995 21:17:01 +0000
parents 3470f1e25a79
children 611d403c7f3d
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1 # Copyright (C) 1995 John W. Eaton
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2 #
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3 # This file is part of Octave.
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4 #
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5 # Octave is free software; you can redistribute it and/or modify it
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6 # under the terms of the GNU General Public License as published by the
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7 # Free Software Foundation; either version 2, or (at your option) any
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8 # later version.
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9 #
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10 # Octave is distributed in the hope that it will be useful, but WITHOUT
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11 # ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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12 # FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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13 # for more details.
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14 #
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15 # You should have received a copy of the GNU General Public License
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16 # along with Octave; see the file COPYING. If not, write to the Free
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17 # Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
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18
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19 function c = fftconv (a, b, N)
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20
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21 # usage: fftconv (a, b [, N])
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22 #
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23 # c = fftconv (a, b) returns the convolution of the vectors a and b,
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24 # a vector with length equal to length (a) + length (b) - 1.
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25 # If a and b are the coefficient vectors of two polynomials, c is
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26 # the coefficient vector of the product polynomial.
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27 #
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28 # The computation uses the FFT by calling fftfilt. If the optional
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29 # argument N is specified, an N-point FFT is used.
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30
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31 # Written by KH (Kurt.Hornik@ci.tuwien.ac.at) on Sep 3, 1994.
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32
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33 if (nargin < 2 || nargin > 3)
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34 usage ("fftconv (b, x [, N])");
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35 endif
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36
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37 if (is_matrix (a) || is_matrix (b))
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38 error ("fftconv: both a and b should be vectors");
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39 endif
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40 la = length (a);
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41 lb = length (b);
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42 if ((la == 1) || (lb == 1))
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43 c = a * b;
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44 else
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45 lc = la + lb - 1;
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46 a(lc) = 0;
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47 b(lc) = 0;
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48 if (nargin == 2)
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49 c = fftfilt (a, b);
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50 else
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51 if !(is_scalar (N))
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52 error ("fftconv: N has to be a scalar");
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53 endif
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54 c = fftfilt (a, b, N);
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55 endif
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56 endif
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57
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58 endfunction