www.pudn.com > geometric.rar > within.m, change:2004-08-13,size:3950b

function result=within(xpt,ypt,xpoly,ypoly) % result = within(xpt,ypt,xpoly,ypoly) % % function returns 1 if (xpt,ypt) is inside the polygon described by % xpoly and ypoly and 0 otherwise % % xpt = x coordinates of the test points. May be a scalar, vector or matrix. % ypt = y coordinates of the test pts % xpoly = vector of the x coordinates of the polygon vertices % The last vertex is tested against the first and is discarded % if it is identical % ypoly = vector of the y coordinates of the polygon vertices % % result = vector of boolean values the same size as xpt(:). Points inside % the polygon may be addressed as xpt(result) and ypt(result) while % those outside are xpt(~result) and ypt(~result) % % Transcribed from FORTAN by G.F. Margrave, October 1993 % FORTRAN written by T.N. Bishop, May 1989 % Algorithm after B.J. Larkin, Computer & Geosciences, Vol 14, pp1-14, 1988 % Original algorithm due to K.R. Anderson, Mathematical Geology, Vol 8, no 1, % 1976, pp 105-106 % % NOTE: It is illegal for you to use this software for a purpose other % than non-profit education or research UNLESS you are employed by a CREWES % Project sponsor. By using this software, you are agreeing to the terms % detailed in this software's Matlab source file. % BEGIN TERMS OF USE LICENSE % % This SOFTWARE is maintained by the CREWES Project at the Department % of Geology and Geophysics of the University of Calgary, Calgary, % Alberta, Canada. The copyright and ownership is jointly held by % its author (identified above) and the CREWES Project. The CREWES % project may be contacted via email at: crewesinfo@crewes.org % % The term 'SOFTWARE' refers to the Matlab source code, translations to % any other computer language, or object code % % Terms of use of this SOFTWARE % % 1) Use of this SOFTWARE by any for-profit commercial organization is % expressly forbidden unless said organization is a CREWES Project % Sponsor. % % 2) A CREWES Project sponsor may use this SOFTWARE under the terms of the % CREWES Project Sponsorship agreement. % % 3) A student or employee of a non-profit educational institution may % use this SOFTWARE subject to the following terms and conditions: % - this SOFTWARE is for teaching or research purposes only. % - this SOFTWARE may be distributed to other students or researchers % provided that these license terms are included. % - reselling the SOFTWARE, or including it or any portion of it, in any % software that will be resold is expressly forbidden. % - transfering the SOFTWARE in any form to a commercial firm or any % other for-profit organization is expressly forbidden. % % END TERMS OF USE LICENSE [m,n]=size(xpoly); if( m~= 1) xpoly = xpoly'; end % make sure we have row vectors [m,n]=size(ypoly); if( m~= 1) ypoly = ypoly'; end % make sure we have row vectors % determine the number of vertices nvert = length(xpoly); if( nvert ~= length(ypoly) ) error( 'xpoly and ypoly must be the same length' ); end % check for last pt == first pt if( (xpoly(1)==xpoly(nvert))&(ypoly(1)==ypoly(nvert))) xpoly = xpoly(1:nvert-1); ypoly = ypoly(1:nvert-1); nvert=nvert-1; end if( nvert < 3 ) error( 'polygon must have more than 2 vertices'); end % count number of polygon sides to the right of the point xprev = [xpoly(nvert) xpoly(1:nvert-1)]; yprev = [ypoly(nvert) ypoly(1:nvert-1)]; xpt=xpt(:);ypt=ypt(:); result=zeros(size(xpt)); % guilty until proven innocent for n=1:length(result) for k=1:nvert test1 = ypt(n) > yprev(k); test2 = ypt(n) <= ypoly(k); if( test1 == test2 ) grad = (xpoly(k)-xprev(k))/(ypoly(k)-yprev(k)); xint = xprev(k) - grad*yprev(k); xcut = grad*ypt(n)+xint; if( xpt(n) < xcut ) result(n) = ~result(n); end end end end