Mercurial > hg > octave-nkf
annotate scripts/general/polyarea.m @ 9245:16f53d29049f
update copyright notices
| author | John W. Eaton <jwe@octave.org> |
|---|---|
| date | Fri, 22 May 2009 10:46:00 -0400 |
| parents | 1bf0ce0930be |
| children | be55736a0783 |
| rev | line source |
|---|---|
| 9245 | 1 ## Copyright (C) 1999, 2006, 2007, 2009 David M. Doolin |
| 5837 | 2 ## |
| 3 ## This file is part of Octave. | |
| 4 ## | |
| 5 ## Octave is free software; you can redistribute it and/or modify it | |
| 6 ## under the terms of the GNU General Public License as published by | |
| 7016 | 7 ## the Free Software Foundation; either version 3 of the License, or (at |
| 8 ## your option) any later version. | |
| 5837 | 9 ## |
| 10 ## Octave is distributed in the hope that it will be useful, but | |
| 11 ## WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
| 13 ## General Public License for more details. | |
| 14 ## | |
| 15 ## You should have received a copy of the GNU General Public License | |
| 7016 | 16 ## along with Octave; see the file COPYING. If not, see |
| 17 ## <http://www.gnu.org/licenses/>. | |
| 5837 | 18 |
| 19 ## -*- texinfo -*- | |
| 20 ## @deftypefn {Function File} {} polyarea (@var{x}, @var{y}) | |
| 21 ## @deftypefnx {Function File} {} polyarea (@var{x}, @var{y}, @var{dim}) | |
| 22 ## | |
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23 ## Determines area of a polygon by triangle method. The variables |
| 5837 | 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 |
| 7001 | 26 ## arrays then the columns of @var{x} and @var{y} are treated separately |
| 5837 | 27 ## and an area returned for each. |
| 28 ## | |
| 29 ## If the optional @var{dim} argument is given, then @code{polyarea} | |
| 30 ## works along this dimension of the arrays @var{x} and @var{y}. | |
| 31 ## | |
| 32 ## @end deftypefn | |
| 33 | |
| 34 ## todo: Add moments for centroid, etc. | |
| 35 ## | |
| 36 ## bugs and limitations: | |
| 37 ## Probably ought to be an optional check to make sure that | |
| 38 ## traversing the vertices doesn't make any sides cross | |
| 39 ## (Is simple closed curve the technical definition of this?). | |
| 40 | |
| 41 ## Author: David M. Doolin <doolin@ce.berkeley.edu> | |
| 5838 | 42 ## Date: 1999-04-14 |
| 5837 | 43 ## Modified-by: |
| 44 ## 2000-01-15 Paul Kienzle <pkienzle@kienzle.powernet.co.uk> | |
| 45 ## * use matlab compatible interface | |
| 46 ## * return absolute value of area so traversal order doesn't matter | |
| 47 ## 2005-10-13 Torsten Finke | |
| 48 ## * optimization saving half the sums and multiplies | |
| 49 | |
| 50 function a = polyarea (x, y, dim) | |
| 51 if (nargin != 2 && nargin != 3) | |
| 52 print_usage (); | |
| 6157 | 53 elseif (size_equal (x, y)) |
| 5837 | 54 if (nargin == 2) |
| 55 a = abs (sum (x .* (shift (y, -1) - shift (y, 1)))) / 2; | |
| 56 else | |
| 57 a = abs (sum (x .* (shift (y, -1, dim) - shift (y, 1, dim)), dim)) / 2; | |
| 58 endif | |
| 5838 | 59 else |
| 60 error ("polyarea: x and y must have the same shape"); | |
| 5837 | 61 endif |
| 62 endfunction | |
| 63 | |
| 64 %!shared x, y | |
| 65 %! x = [1;1;3;3;1]; | |
| 66 %! y = [1;3;3;1;1]; | |
| 67 %!assert (polyarea(x,y), 4, eps) | |
| 68 %!assert (polyarea([x,x],[y,y]), [4,4], eps) | |
| 69 %!assert (polyarea([x,x],[y,y],1), [4,4], eps) | |
| 70 %!assert (polyarea([x,x]',[y,y]',2), [4;4], eps) |