Check if a matrix is ​​a identity matrix in Matlab

Question

I need to check if the matrix is ​​a identity matrix. I know that there is a function that checks if the matrix is ​​a diagonal matrix, i.e. isdiag . I know that I can do the following to check if matrix a is a identity matrix:

 isequal(a, eye(size(a, 1))) 

Is there a function like isdiag tha does this directly for me?

Answer 1

 sum(sum(A - eye(size(A,1)) < epsilon)) == 0 

Subtract your identity and check for more items than epsilon.

Answer 2

As others have said, you do not necessarily want to verify exact equality with the identity matrix. In addition, using eye can potentially consume unnecessary memory for large enough matrices. I would recommend using diag to get around this.

 isdiag(a) && all(abs(diag(a) - 1) < tolerance)