manolas
/
vcglib
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

Add covariance matrix of a set of points

This commit is contained in:
ganovelli 2008-08-07 18:33:23 +00:00
parent 82d9dec26a
commit 1e94f7cf46
1 changed files with 24 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

24
vcg/math/matrix33.h
View File

@ -517,6 +517,30 @@ ScalarType Norm()
return (math::Sqrt(SQsum));
}
/*
It compute the covariance matrix of a set of 3d points. Returns the barycenter
*/
template <class STLPOINTCONTAINER >
void Covariance(const STLPOINTCONTAINER &points, Point3<S> &bp) {
assert(!points.empty());
typedef typename STLPOINTCONTAINER::const_iterator PointIte;
// first cycle: compute the barycenter
bp.Zero();
for( PointIte pi = points.begin(); pi != points.end(); ++pi) bp+= (*pi);
bp/=points.size();
// second cycle: compute the covariance matrix
this->SetZero();
vcg::Matrix33<ScalarType> A;
for( PointIte pi = points.begin(); pi != points.end(); ++pi) {
Point3<S> p = (*pi)-bp;
A.OuterProduct(p,p);
(*this)+= A;
}
}
/*
It compute the cross covariance matrix of two set of 3d points P and X;
it returns also the barycenters of P and X.