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maint: Update copyright notices for 2015.
author John W. Eaton <jwe@octave.org>
date Wed, 11 Feb 2015 14:19:08 -0500
parents d63878346099
children 7503499a252b
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19898
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1 ## Copyright (C) 1999-2015 David M. Doolin
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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} {} polyarea (@var{x}, @var{y})
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21 ## @deftypefnx {Function File} {} polyarea (@var{x}, @var{y}, @var{dim})
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22 ##
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23 ## Determine area of a polygon by triangle method. The variables
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24 ## @var{x} and @var{y} define the vertex pairs, and must therefore have
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25 ## the same shape. They can be either vectors or arrays. If they are
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26 ## arrays then the columns of @var{x} and @var{y} are treated separately
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27 ## and an area returned for each.
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28 ##
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29 ## If the optional @var{dim} argument is given, then @code{polyarea}
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30 ## works along this dimension of the arrays @var{x} and @var{y}.
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31 ##
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32 ## @end deftypefn
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33
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34 ## todo: Add moments for centroid, etc.
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35 ##
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36 ## bugs and limitations:
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37 ## Probably ought to be an optional check to make sure that
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38 ## traversing the vertices doesn't make any sides cross
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39 ## (Is simple closed curve the technical definition of this?).
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40
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41 ## Author: David M. Doolin <doolin@ce.berkeley.edu>
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42 ## Date: 1999-04-14
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43 ## Modified-by:
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44 ## 2000-01-15 Paul Kienzle <pkienzle@kienzle.powernet.co.uk>
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45 ## * use matlab compatible interface
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46 ## * return absolute value of area so traversal order doesn't matter
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47 ## 2005-10-13 Torsten Finke
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48 ## * optimization saving half the sums and multiplies
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49
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50 function a = polyarea (x, y, dim)
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51 if (nargin != 2 && nargin != 3)
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52 print_usage ();
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53 elseif (size_equal (x, y))
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54 if (nargin == 2)
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55 a = abs (sum (x .* (shift (y, -1) - shift (y, 1)))) / 2;
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56 else
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57 a = abs (sum (x .* (shift (y, -1, dim) - shift (y, 1, dim)), dim)) / 2;
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58 endif
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59 else
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60 error ("polyarea: X and Y must have the same shape");
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61 endif
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62 endfunction
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63
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64
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65 %!shared x, y
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66 %! x = [1;1;3;3;1];
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67 %! y = [1;3;3;1;1];
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68 %!assert (polyarea (x,y), 4, eps)
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69 %!assert (polyarea ([x,x],[y,y]), [4,4], eps)
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70 %!assert (polyarea ([x,x],[y,y],1), [4,4], eps)
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71 %!assert (polyarea ([x,x]',[y,y]',2), [4;4], eps)
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