Matlab says the matrix is not symmetric

Hi!

I compute the following matrix: D = b'Ab, where A is a symmetric covariance matrix. D is high-dimensional and must be symmetric by definition.

But when I apply a functiion "issymmetric" to D, Matlab returns 0 meaning that it is not symmetric.

I guess the problem is the way Matlab handles calculations. But how to fix it and make sure that Matlab sees the symmetry of the matrix D?

Thank you in advance!

Answer 1

[John D'Errico]

D = rand(100);
D = (D + D.')/2;

issymmetric(D)
ans =
  logical
   1

[Elena]

Thanks a lot!