@Carl Love you're right! now I can find them, thanks a lot

@Carl Love something like this:

@acer thanks, it's fixed now

@Carl Love by bidiagonal I mean there's another diagonal below the main one, but in this case, I want to find the eigenvalues of C which is composed of this simple bidiagonal matrix, its transposed matrix and zero matrices, so actually the main diagonal of C contains only zeros and I want the QR alg. to sort the eigenvalues into the main diagonal of C

@acer yes