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annotate scripts/signal/fftconv.m @ 787:c5d35bb139b6

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[project @ 1994-10-11 00:34:13 by jwe] Initial revision
author jwe
date Tue, 11 Oct 1994 00:34:39 +0000
parents
children 3470f1e25a79
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1 function c = fftconv (a, b, N)
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2
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3 # usage: fftconv (a, b [, N])
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4 #
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5 # c = fftconv (a, b) returns the convolution of the vectors a and b,
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6 # a vector with length equal to length (a) + length (b) - 1.
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7 # If a and b are the coefficient vectors of two polynomials, c is
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8 # the coefficient vector of the product polynomial.
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9 #
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10 # The computation uses the FFT by calling fftfilt. If the optional
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11 # argument N is specified, an N-point FFT is used.
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12
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13 # Written by KH (Kurt.Hornik@ci.tuwien.ac.at) on Sep 3, 1994
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14 # Copyright Dept of Statistics and Probability Theory TU Wien
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15
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16 if (nargin < 2 || nargin > 3)
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17 error ("usage: fftconv (b, x [, N])");
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18 endif
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19
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20 if (is_matrix (a) || is_matrix (b))
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21 error ("fftconv: both a and b should be vectors");
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22 endif
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23 la = length (a);
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24 lb = length (b);
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25 if ((la == 1) || (lb == 1))
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26 c = a * b;
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27 else
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28 lc = la + lb - 1;
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29 a(lc) = 0;
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30 b(lc) = 0;
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31 if (nargin == 2)
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32 c = fftfilt (a, b);
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33 else
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34 if !(is_scalar (N))
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35 error ("fftconv: N has to be a scalar");
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36 endif
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37 c = fftfilt (a, b, N);
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38 endif
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39 endif
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40
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41 endfunction