Make an existing matrix symmetric

Hi there,

I've have a function where I take a matrix M as an input and return a value based on if it's symmetric or not. I would like to extend this function by altering the input matrix to make it symmetric. How can I make an asymmetric matrix symmetric by altering it?

Thank you

Answer 1

[Walter Roberson]

(M + M.')/2

This is a useful technical when you have values that are intended to be symmetric but which turn out not to be due to round-off error.

[N/A]

Thank you. As a solution, what I have done is M + M^T which is always symmetric.

[Walter Roberson]

Consider that M+M.' will turn the identity matrix into a matrix that has 2 along the main diagonal. It will be symmetric, yes, but you are also changing the values of matrices that start out symmetric.