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sind.m: Overhaul function for improved accuracy with large inputs. * sind.m: More explicitly describe the advantage of sind() in documentation. Unwrap input in to domain [0, 360) which improves accuracy for large arguments. Zero out inputs which are a multiple of 180 degrees before calling sin() function for improved performance. Expand BIST tests.
author Rik <rik@octave.org>
date Mon, 07 Dec 2020 17:32:04 -0800
parents 90fea9cc9caa
children 9193e7c990ea
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1 ########################################################################
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2 ##
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3 ## Copyright (C) 2006-2020 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 {} {} sind (@var{x})
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28 ## Compute the sine for each element of @var{x} in degrees.
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29 ##
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30 ## The function is more exact than @code{sin} for multiples of 180 degrees and
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31 ## returns zero rather than a small value on the order of eps.
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32 ## @seealso{asind, sin}
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33 ## @end deftypefn
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35 function y = sind (x)
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36
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37 if (nargin < 1)
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38 print_usage ();
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39 endif
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40
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41 ## Unwrap multiples so that new domain is [0, 360)
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42 x = mod (x, 360);
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43
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44 ## Integer multiples of pi must be exactly zero
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45 x(x == 180) = 0;
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46
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47 y = sin (x / 180 * pi);
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48
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49 endfunction
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50
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52 %!assert (sind (10:20:360), sin ([10:20:360] * pi/180), 5*eps)
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53 %!assert (sind ([-360, -180, 0, 180, 360]) == 0)
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54 %!assert (sind ([-270, -90, 90, 270]), [1, -1, 1, -1])
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55
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56 %!error <Invalid call> sind ()