annotate scripts/signal/hanning.m @ 20026:230c1e2a678d

blackman, hamming, hanning: Simplify handling of periodic window option * blackman.m, hamming.m, hanning.m: Simplify logic for handling periodic or symmetric window option.
author Mike Miller <mtmiller@octave.org>
date Sat, 04 Apr 2015 14:12:10 -0400
parents d209fbae38ae
children f1d0f506ee78
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1 ## Copyright (C) 1995-2015 Andreas Weingessel
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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 3 of the License, or (at
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8 ## your option) 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, see
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17 ## <http://www.gnu.org/licenses/>.
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18
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19 ## -*- texinfo -*-
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20 ## @deftypefn {Function File} {} hanning (@var{m})
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21 ## @deftypefnx {Function File} {} hanning (@var{m}, "periodic")
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22 ## @deftypefnx {Function File} {} hanning (@var{m}, "symmetric")
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23 ## Return the filter coefficients of a Hanning window of length @var{m}.
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24 ##
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25 ## If the optional argument @qcode{"periodic"} is given, the periodic form
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26 ## of the window is returned. This is equivalent to the window of length
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27 ## @var{m}+1 with the last coefficient removed. The optional argument
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28 ## @qcode{"symmetric"} is equivalent to not specifying a second argument.
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29 ##
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30 ## For a definition of the Hanning window, see e.g.,
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31 ## @nospell{A.V. Oppenheim & R. W. Schafer},
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32 ## @cite{Discrete-Time Signal Processing}.
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33 ## @end deftypefn
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34
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35 ## Author: AW <Andreas.Weingessel@ci.tuwien.ac.at>
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36 ## Description: Coefficients of the Hanning window
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37
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38 function c = hanning (m, opt)
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39
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40 if (nargin < 1 || nargin > 2)
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41 print_usage ();
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42 endif
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43
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44 if (! (isscalar (m) && (m == fix (m)) && (m > 0)))
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45 error ("hanning: M must be a positive integer");
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46 endif
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47
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48 N = m - 1;
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49 if (nargin == 2)
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50 switch (opt)
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51 case "periodic"
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52 N = m;
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53 case "symmetric"
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54 ## Default option, same as no option specified.
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55 otherwise
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56 error ('hanning: window type must be either "periodic" or "symmetric"');
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57 endswitch
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58 endif
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59
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60 if (m == 1)
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61 c = 1;
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62 else
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63 m = m - 1;
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64 c = 0.5 - 0.5 * cos (2 * pi * (0 : m)' / N);
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65 endif
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66
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67 endfunction
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70 %!assert (hanning (1), 1);
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71 %!assert (hanning (2), zeros (2,1));
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72 %!assert (hanning (15), flip (hanning (15)), 5*eps);
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73 %!assert (hanning (16), flip (hanning (16)), 5*eps);
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74 %!test
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75 %! N = 15;
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76 %! A = hanning (N);
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77 %! assert (A(ceil (N/2)), 1);
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78
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79 %!assert (hanning (15), hanning (15, "symmetric"));
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80 %!assert (hanning (16)(1:15), hanning (15, "periodic"));
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81 %!test
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82 %! N = 16;
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83 %! A = hanning (N, "periodic");
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84 %! assert (A(N/2 + 1), 1);
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85
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86 %!error hanning ()
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87 %!error hanning (0.5)
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88 %!error hanning (-1)
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89 %!error hanning (ones (1,4))
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90 %!error hanning (1, "invalid");
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91