
Re: why the sigma of symmetrical svd for a real symmetric matrix is negative?
Posted:
Dec 26, 2012 11:39 PM


"Rick" wrote in message <kbgbi5$g5n$1@newscl01ah.mathworks.com>... > as we know, for a real symmetric matrix A, A, there exists a singular value decomposition as A=USU', and S should be a rectangular diagonal matrix with nonnegative real numbers on the diagonal. But when I use the command schur(), > it seems that S appears negative real numbers on the diagonal as the following. Is there any problem?           Unless your A matrix is positive definite there is no reason its singular value and schur decompositions should be the same, and the A you have defined is certainly not positive definite. In fact all its eigenvalues are negative. Check the Wikipedia site:
http://en.wikipedia.org/wiki/Schur_decomposition
Roger Stafford

