[Gretl-users] idempotence and symmetry

Dear Gretl users, I know my question may seem (it actually is) very banal, but I can't figure out a way to check if two matrices are equal. The point is verifying idempotence and symmetry for an orthogonal projector. The mathematical proof isn't required here: the point is showing that the actual calculated matrices are orthogonal projectors and therefore have the specified properties; I got to show the numbers are the same. And apart from arbitrary extraction of submatrices to prove they get out same, I can't think of anything 'scientific'. Hope you will be able to help me with the matter. Regards, SP