How to get 'extra' information from convhulln

Hi all,

I am using the convhulln function to calculate the convex hull c and the volume V of a set of n-dimensional data x Convhulln uses the qhull library (<http://www.qhull.org/)>.

I would like to know the sum of the area's of all facets of this convex hull. According to the documentation of QHULL, this can be achieved by sending the option FA along with the data. (sourc: http://www.qhull.org/html/qh-optf.htm#FA)

The problem now is that this data does not show when calling the function like this:

[c, V] = convhulln(x,{'FA'});

According to this same documentation, the area should be printed in the summary of the results. How do I access this summary? Is this possible through the convhulln function?

Thanks in advance

Answer 1

[John D'Errico]

No, you cannot return the area. Just because qhull CAN return that information if you were to call it directly, the MATLAB code does not return that information. It is not provided.

That does not say it is difficult to compute the area. In fact, this is quite easy, since you have all the information needed. You don't say what n is, so I can't answer that part.

[M. F.]

Thanks for the quick response!

Perhaps I'll try to connect with QHULL myself then.

[R. N.]

How would you compute the area for n=4 and n=6?