【转】判断点在多边形内（matlab）

inpolygon -Points inside polygonal region

Syntax

IN = inpolygon(X,Y,xv,yv)
[IN ON] = inpolygon(X,Y,xv,yv)

Description

IN = inpolygon(X,Y,xv,yv) returns a matrix IN the same size as X and Y. Each element of IN is assigned the value 1 or 0 depending on whether the point (X(p,q),Y(p,q)) is inside the polygonal region whose vertices are specified by the vectors xv and yv. In particular:

IN(p,q) = 1	If (X(p,q),Y(p,q)) is inside the polygonal region or on the polygon boundary
IN(p,q) = 0	If (X(p,q),Y(p,q)) is outside the polygonal region

[IN ON] = inpolygon(X,Y,xv,yv) returns a second matrix ON the same size as X and Y. Each element of ON is assigned the value 1 or 0 depending on whether the point (X(p,q),Y(p,q)) is on the boundary of the polygonal region whose vertices are specified by the vectors xv and yv. In particular:

ON(p,q) = 1	If (X(p,q),Y(p,q)) is on the polygon boundary
ON(p,q) = 0	If (X(p,q),Y(p,q)) is inside or outside the polygon boundary

Examples

L = linspace(0,2.*pi,6); xv = cos(L)';yv = sin(L)'; xv = [xv ; xv(1)]; yv = [yv ; yv(1)]; x = randn(250,1); y = randn(250,1); in = inpolygon(x,y,xv,yv); plot(xv,yv,x(in),y(in),'r+',x(~in),y(~in),'bo')