point in convex hull?
62 vues (au cours des 30 derniers jours)
Afficher commentaires plus anciens
how compute if a point point is inside the convex hull ?
0 commentaires
Réponse acceptée
Friedrich
le 23 Mar 2012
Hi,
I would use convhull and inpolygon:
xx = -1:.05:1; yy = abs(sqrt(xx));
[x,y] = pol2cart(xx,yy);
k = convhull(x,y);
hold on
plot(x(k),y(k),'r-',x,y,'b+')
x_test = rand(10,1);
y_test = rand(10,1);
IN = inpolygon(x_test,y_test,x(k),y(k))
plot(x_test(IN),y_test(IN),'g*',x_test(~IN),y_test(~IN),'y*')
hold off
2 commentaires
Friedrich
le 23 Mar 2012
This wont work in higher dimensions. You have to do some smart geometry stuff to get the information you like. you can use convhulln to get the facets of your convex hull and also the corners (x_i, i = 1..m). After that try to get coefficients a_i > 0 so that
sum_i x_i*a_i = v where sum_i a_i = 1 (basically that's the definition of the convex hull). (v is the vector you like to know if its inside or outside of the convex hull). Finding one solution for the system of equations is easy, but the condition that the sum over the coefficients gives 1 is pretty tricky. I don't know if there is an easy way to get solve this.
Seems more like a mathematical question rather than a MATLAB question for me.
If you know an algorithm come back and ask how to implement/use this in MATLAB. But first you need to know how to check this in theory before doing it in MATLAB.
Plus de réponses (1)
Matt Kindig
le 23 Mar 2012
There is a file on the File Exchange called 'inhull'. I have used it for precisely this purpose.
2 commentaires
Voir également
Catégories
En savoir plus sur Bounding Regions dans Help Center et File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!