If you have a polygon pgon, of unknown size, get the number of vertices:
pgon=polyshape(cosd(0:40:320),sind(0:40:320));
plot(pgon); hold on; axis equal; axis tight
N=length(pgon.Vertices);
fprintf('Number of vertices=%d.\n',N)
Use N to select vertices randomly:
vpair=randi(N,[1,2]); %return 2 random numers between 1 and N inclusive
Draw a line beteween the 2 vertices
plot(pgon.Vertices(vpair,1),pgon.Vertices(vpair,2),'-r')
The randomly chosen pair could be the same vertex twice, or adjacent vertices. You could add code to prevent this.
Good luck.
