www.pudn.com > geometric.rar > inside.m, change:2004-08-13,size:3843b

function result=inside(xpt,ypt,xpoly,ypoly)  % result = inside(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