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matlabsymbolic-mathmatlab-compiler

SVD on a symbolic matrix on Matlab

I'm trying to calculate the SVD on this symbolic matrix using Matlab

0 2 3 4*a 5*a
6 7 1 8*a 9*a

using the following code:

syms a
M = [0 2 3 4*a 5*a ; 6 7 1 8*a 9*a]
s = svd(M)

It's working, and i can get the singular values, but using the following code I can get the orthogonal matrices.

[U,S,V] = svd(M)

I get this error:

Error using sym/svd (line 85) Input arguments must be convertible to floating-point numbers.

How can i deal with that?

Solution

  • From the docs (emphasis mine):

    [U,S,V] = svd(A) returns numeric unitary matrices U and V with the columns containing the singular vectors, and a diagonal matrix S containing the singular values. The matrices satisfy the condition A = USV', where V' is the Hermitian transpose (the complex conjugate transpose) of V. The singular vector computation uses variable-precision arithmetic. svd does not compute symbolic singular vectors. Therefore, the input matrix A must be convertible to floating-point numbers. For example, it can be a matrix of symbolic numbers.

    So simply, you cant. It's not supported.