Drexel dragonThe Math ForumDonate to the Math Forum


Math Forum
 Ask Dr. Math
 Discussions
 Internet Newsletter
 MathTools
 Problems of the Week
 Teacher2Teacher
 Teacher Exchange
 Workshops

Search All of the Math Forum:
Browse our Internet Mathematics Library

Views expressed in these public forums are not endorsed by Drexel University or The Math Forum.


Math Forum » Discussions » Software » comp.soft-sys.matlab

Topic: why the sigma of symmetrical svd for a real symmetric matrix is negative?
Replies: 4   Last Post: Dec 27, 2012 7:30 PM

Advanced Search
Reply to this Topic Reply to this Topic

Back to Topic List Back to Topic List Jump to Tree View Jump to Tree View   Messages: [ Previous | Next ]
Rick

Posts: 1
Registered: 12/26/12
why the sigma of symmetrical svd for a real symmetric matrix is negative?
Posted: Dec 26, 2012 9:25 PM
  Click to see the message monospaced in plain text Plain Text   Click to reply to this topic Reply

Hi everyone,
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?

Thanks a lots!


>>A=
-1.3410 0.5350 0.2995 -1.1138
0.5350 -2.5191 -0.1422 0.4953
0.2995 -0.1422 -1.4695 0.2981
-1.1138 0.4953 0.2981 -2.2897

>>[u,s]=schur(A)

u =

-0.4768 -0.2191 0.0448 0.8501
0.5549 -0.8260 0.0177 0.0974
0.1944 0.1630 0.9621 0.1004
-0.6534 -0.4931 0.2685 -0.5078


s =

-3.6119 0 0 0
0 -2.0534 0 0
0 0 -1.3749 0
0 0 0 -0.5790

Point your RSS reader here for a feed of the latest messages in this topic.

[Privacy Policy] [Terms of Use]

© Drexel University 1994-2013. All Rights Reserved.
The Math Forum is a research and educational enterprise of the Drexel University School of Education.