Points Inside polygone

Finds those points (xi,yi) who are inside the polygon, defined by the vectors (x,y)

Description

Find those points (xi,yi) who are inside the polygone defined by the vectors (x,y).

Syntax: [xin,yin,Ind]=Inside(X,Y,xi,yi)

where Ind is the index of (xi,yi) that are inside the polygone
 
Example:
  
  %--- create polygone (x,y)
  phi=linspace(0,2*pi,50);
  X=(1+0.2*sin(6*phi)).*cos(phi);
  Y=(1+0.2*sin(6*phi)).*sin(phi);
  %--- random points (xi,yi)
  Nr=20;
  xi=randn(1,Nr);yi=randn(1,Nr);
  [xin,yin,Ind]=Inside(X,Y,xi,yi);
  %--- plot
  plot(X,Y,X,Y,'.',xi,yi,'ro',xin,yin,'b.');axis equal;

• MATLAB release: MATLAB 6.5 (R13)

[gok gok]

its not working with number of points more then 200. Did crashed with 2000 points at line 46:
dotpr=dot([Dxic;Dyic;0*Dxic],norm(:,CInd));

[Urs Schwarz (us)]

per, what exactly is the difference to ML's generic inpolygon?
best
urs

[John D'Errico]

This code does not do what it claims. Rather than find points inside a polygon, it approximates the polygon with 300 points along a spline fit, then tries to find points inside that boundary. The spline fit chosen is a poor one, not based on arc length, but assuming the points on the polygon are equidistant from their neighbors. It will be very slow for larger sets of points, even crashing for reasonable sets of data. Use inpolygon from matlab itself instead.