From 8a8eb6fb6598508a84e19f0a5f00185eab0def7e Mon Sep 17 00:00:00 2001
From: cnr-isti-vclab <paolo.cignoni@isti.cnr.it>
Date: Fri, 24 Oct 2008 17:21:53 +0000
Subject: [PATCH] add the possiblity to sort eigenvalues/vectors according to
their absolute values
---
vcg/math/lin_algebra.h | 32 +++++++++++++++++++++++---------
1 file changed, 23 insertions(+), 9 deletions(-)
diff --git a/vcg/math/lin_algebra.h b/vcg/math/lin_algebra.h
index 01eeb108..b9e07ecc 100644
--- a/vcg/math/lin_algebra.h
+++ b/vcg/math/lin_algebra.h
@@ -169,23 +169,37 @@ namespace vcg
/*!
* Given the eigenvectors and the eigenvalues as output from JacobiRotate, sorts the eigenvalues
* into descending order, and rearranges the columns of v correspondinlgy.
- /param eigenvalues
- /param eigenvector (in columns)
+ * \param eigenvalues
+ * \param eigenvector (in columns)
+ * \param absComparison sort according to the absolute values of the eigenvalues.
*/
template < typename MATRIX_TYPE, typename POINT_TYPE >
- void SortEigenvaluesAndEigenvectors(POINT_TYPE &eigenvalues, MATRIX_TYPE &eigenvectors)
+ void SortEigenvaluesAndEigenvectors(POINT_TYPE &eigenvalues, MATRIX_TYPE &eigenvectors, bool absComparison = false)
{
assert(eigenvectors.ColumnsNumber()==eigenvectors.RowsNumber());
int dimension = eigenvectors.ColumnsNumber();
int i, j, k;
- float p;
+ float p,q;
for (i=0; i<dimension-1; i++)
{
- p = eigenvalues[ k=i ];
-
- for (j=i+1; j<dimension; j++)
- if (eigenvalues[j] >= p)
- p = eigenvalues[ k=j ];
+ if (absComparison)
+ {
+ p = fabs(eigenvalues[k=i]);
+ for (j=i+1; j<dimension; j++)
+ if ((q=fabs(eigenvalues[j])) >= p)
+ {
+ p = q;
+ k = j;
+ }
+ p = eigenvalues[k];
+ }
+ else
+ {
+ p = eigenvalues[ k=i ];
+ for (j=i+1; j<dimension; j++)
+ if (eigenvalues[j] >= p)
+ p = eigenvalues[ k=j ];
+ }
if (k != i)
{