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1 ## Copyright (C) 1996, 1997 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 |
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7 ## the Free Software Foundation; either version 2, or (at your option) |
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8 ## any later version. |
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9 ## |
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10 ## Octave is distributed in the hope that it will be useful, but |
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11 ## WITHOUT ANY WARRANTY; without even the implied warranty of |
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12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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13 ## General Public License 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, 59 Temple Place - Suite 330, Boston, MA |
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18 ## 02111-1307, USA. |
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19 |
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20 ## -*- texinfo -*- |
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21 ## @deftypefn {Function File} {} fftconv (@var{a}, @var{b}, @var{n}) |
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22 ## Return the convolution of the vectors @var{a} and @var{b}, as a vector |
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23 ## with length equal to the @code{length (a) + length (b) - 1}. If @var{a} |
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24 ## and @var{b} are the coefficient vectors of two polynomials, the returned |
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25 ## value is the coefficient vector of the product polynomial. |
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26 ## |
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27 ## The computation uses the FFT by calling the function @code{fftfilt}. If |
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28 ## the optional argument @var{n} is specified, an N-point FFT is used. |
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29 ## @end deftypefn |
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30 |
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31 ## Author: KH <Kurt.Hornik@ci.tuwien.ac.at> |
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32 ## Created: 3 September 1994 |
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33 ## Adapted-By: jwe |
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34 |
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35 function c = fftconv (a, b, N) |
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36 |
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37 if (nargin < 2 || nargin > 3) |
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38 usage ("fftconv (b, x, N)"); |
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39 endif |
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40 |
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41 if (! (isvector (a) && isvector (b))) |
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42 error ("fftconv: both a and b should be vectors"); |
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43 endif |
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44 la = length (a); |
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45 lb = length (b); |
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46 if ((la == 1) || (lb == 1)) |
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47 c = a * b; |
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48 else |
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49 lc = la + lb - 1; |
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50 a(lc) = 0; |
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51 b(lc) = 0; |
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52 if (nargin == 2) |
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53 c = fftfilt (a, b); |
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54 else |
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55 if (! (isscalar (N))) |
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56 error ("fftconv: N has to be a scalar"); |
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57 endif |
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58 c = fftfilt (a, b, N); |
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59 endif |
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60 endif |
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61 |
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62 endfunction |
