I want to use SVD directly in Sage, is it possible?
from http://wiki.sagemath.org/interact/lin..., I know that, we can...
sage: from scipy import linalg
sage: U,s,Vh = linalg.svd(A) # A is a fixed matrix, e.g., A = [1, 2; 3, 4]
Thanks in advance!
It depends on the ring of the matrix. For example, it works for matrices over CDF:
sage: M = matrix(CDF, [[1,2,3],[1,4,6]])
sage: M.SVD()
(
[-0.455252372951 -0.890362441325]
[-0.890362441325 0.455252372951],
[ 8.17345734477 0.0 0.0]
[ 0.0 0.441129270439 0.0],
[ -0.164632267291 -0.986355015482 -2.81388521797e-16]
[ -0.547131320636 0.0913215509714 -0.832050294338]
[ -0.820696980953 0.136982326457 0.554700196225]
)
but not for matrices over QQ:
sage: M = matrix(QQ, [[1,2,3],[1,4,6]])
sage: M.SVD()
AttributeError: 'sage.matrix.matrix_rational_dense.Matrix_rational_dense' object has no attribute 'SVD'
So, the method .SVD() is not implemented for every kind of matrices.
Asked: 2013-11-07 11:13:41 +0100
Seen: 5,075 times
Last updated: Nov 07 '13
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Can you explain what you mean by use SVD directly? The commands you mentioned is the way to use SVD. Is there any other way you wish to do it?