Hi,
I have a project which asks me to compute eigenvalue and eigenvector using stiffness matrix and mass matrix got from NASTRAN.
But now I have problem to remove the Rows and Columns where entries are all zero.
Is there some ways to make it?
Thanks.

You can compute and apply one (or two) PermutationMatrix to put all non-empty rows/columns in the top-left-corner, and then call conservative resize to squeeze the empty rows/cols.