POLYGONAREA Calculate the area of a polygon Inputs: P(n,2) is the polygon vertices Outputs: A is teh area of teh polygon The area is positive if the vertices go anti-clockwise around the polygon.

0001 function a=polygonarea(p) 0002 %POLYGONAREA Calculate the area of a polygon 0003 % 0004 % Inputs: 0005 % P(n,2) is the polygon vertices 0006 % 0007 % Outputs: 0008 % A is teh area of teh polygon 0009 % 0010 % The area is positive if the vertices go anti-clockwise around the polygon. 0011 % 0012 0013 % Copyright (C) Mike Brookes 2009 0014 % Version: $Id: polygonarea.m 713 2011-10-16 14:45:43Z dmb $ 0015 % 0016 % VOICEBOX is a MATLAB toolbox for speech processing. 0017 % Home page: http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/voicebox.html 0018 % 0019 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 0020 % This program is free software; you can redistribute it and/or modify 0021 % it under the terms of the GNU General Public License as published by 0022 % the Free Software Foundation; either version 2 of the License, or 0023 % (at your option) any later version. 0024 % 0025 % This program is distributed in the hope that it will be useful, 0026 % but WITHOUT ANY WARRANTY; without even the implied warranty of 0027 % MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 0028 % GNU General Public License for more details. 0029 % 0030 % You can obtain a copy of the GNU General Public License from 0031 % http://www.gnu.org/copyleft/gpl.html or by writing to 0032 % Free Software Foundation, Inc.,675 Mass Ave, Cambridge, MA 02139, USA. 0033 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 0034 p(end+1,:)=p(1,:); % append an extra point 0035 a=0.5*sum((p(1:end-1,1)-p(2:end,1)).*(p(1:end-1,2)+p(2:end,2)),1); 0036 if ~nargout 0037 plot(p(:,1),p(:,2),'b-'); 0038 mnx=[1.05 -0.05;-0.05 1.05]*[min(p);max(p)]; 0039 set(gca,'xlim',mnx(:,1)','ylim',mnx(:,2)'); 0040 title(sprintf('Area = %.2g',a)); 0041 end

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