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NEWS.9.md: Fix typo and minor formatting changes. * etc/NEWS.9.md: Fix typo. Adjust whitespace. Use markdown syntax for code snippets.
author Markus Mützel <markus.muetzel@gmx.de>
date Wed, 05 Jun 2024 11:27:35 +0200
parents 2e484f9f1f18
children
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1 ########################################################################
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2 ##
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3 ## Copyright (C) 2020-2024 The Octave Project Developers
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4 ##
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5 ## See the file COPYRIGHT.md in the top-level directory of this
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6 ## distribution or <https://octave.org/copyright/>.
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7 ##
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8 ## This file is part of Octave.
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9 ##
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10 ## Octave is free software: you can redistribute it and/or modify it
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11 ## under the terms of the GNU General Public License as published by
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12 ## the Free Software Foundation, either version 3 of the License, or
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13 ## (at your option) any later version.
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14 ##
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15 ## Octave is distributed in the hope that it will be useful, but
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16 ## WITHOUT ANY WARRANTY; without even the implied warranty of
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17 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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18 ## GNU General Public License for more details.
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19 ##
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20 ## You should have received a copy of the GNU General Public License
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21 ## along with Octave; see the file COPYING. If not, see
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22 ## <https://www.gnu.org/licenses/>.
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23 ##
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24 ########################################################################
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25
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26 ## -*- texinfo -*-
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27 ## @deftypefn {} {@var{y} =} sinpi (@var{x})
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28 ## Compute sine (@var{x} * pi) for each element of @var{x} accurately.
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29 ##
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30 ## The ordinary @code{sin} function uses IEEE floating point numbers and may
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31 ## produce results that are very close (within a few eps) of the correct
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32 ## value, but which are not exact. The @code{sinpi} function is more accurate
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33 ## and returns 0 exactly for integer values of @var{x} and +1/-1 for
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34 ## half-integer values (e.g., @dots{}, -3/2, -1/2, 1/2, 3/2, @dots{}).
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35 ##
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36 ## Example @*
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37 ## comparison of @code{sin} and @code{sinpi} for integer values of @var{x}
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38 ##
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39 ## @example
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40 ## @group
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41 ## sin ([0, 1, 2, 3] * pi)
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42 ## @result{}
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43 ## 0 1.2246e-16 -2.4493e-16 3.6739e-16
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44 ##
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45 ## sinpi ([0, 1, 2, 3])
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46 ## @result{}
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47 ## 0 0 0 0
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48 ## @end group
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49 ## @end example
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50 ##
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51 ## @seealso{cospi, sin}
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52 ## @end deftypefn
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53
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54 function y = sinpi (x)
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55
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56 if (nargin < 1)
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57 print_usage ();
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58 endif
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59
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60 ## Wrap integer multiples so that new domain is [-1, 1)
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61 x = mod (x-1, 2) - 1;
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62
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63 ## Integer multiples of pi must be exactly zero
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64 x(x == -1) = 0;
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65
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66 y = sin (x * pi);
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67
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68 endfunction
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69
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70
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71 %!assert (sinpi ([-1, -2, 0, 1, 2]) == 0)
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72 %!assert (sinpi ([-3/2, -1/2, 1/2, 3/2]), [1, -1, 1, -1])
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73 %!assert (sinpi (100 + [0.1:0.1:0.9]), sin ([0.1:0.1:0.9]*pi), 2*eps (100))
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74
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75 %!error <Invalid call> sinpi ()