[Toon-members] TooN SymEigen.h

[Damian Eads]

CVSROOT:        /sources/toon
Module name:    TooN
Changes by:     Damian Eads <eads>      09/08/27 11:11:18

Modified files:
        .              : SymEigen.h 

Log message:
        Added matrix square root.

CVSWeb URLs:
http://cvs.savannah.gnu.org/viewcvs/TooN/SymEigen.h?cvsroot=toon&r1=1.19&r2=1.20

Patches:
Index: SymEigen.h
===================================================================
RCS file: /sources/toon/TooN/SymEigen.h,v
retrieving revision 1.19
retrieving revision 1.20
diff -u -b -r1.19 -r1.20
--- SymEigen.h  26 Aug 2009 07:49:20 -0000      1.19
+++ SymEigen.h  27 Aug 2009 11:11:18 -0000      1.20
@@ -265,6 +265,18 @@
                return det;
        }
 
+       /// Calculate the square root M=sqrt(A) of a matrix, which is
+       /// the matrix M such that M.T*M=sqrt(A).
+       Matrix<Size, Size, Precision> get_sqrtm () const {
+               Vector<Size, Precision> Dsqrt(my_evalues.size());
+               // In the future, maybe throw an exception if an
+               // eigenvalue is negative?
+               for (int i = 0; i < my_evalues.size(); ++i) {
+                       Dsqrt[i] = std::sqrt(my_evalues[i]);
+               }
+               return my_evectors.T() * diagmult(Dsqrt, my_evectors);
+       }
+
 private:
        // eigen vectors laid out row-wise so evectors[i] is the ith evector
        Matrix<Size,Size,Precision> my_evectors;