So, using MATLAB, I'm trying to create the block diagonal matrix for the central difference approximation to the 2D laplacian operator in rectangular coordinates, and I've stumbled on to what looks like a pretty useful function. It's called "blkdiag", and it works by taking all of the input arguments, which are matrices, and placing them on the diagonal of a larger sparse matrix. The problem I have with this function however, is that it doesn't create a block diagonal matrix of arbitrary size--it only concatenates the numer of arguments you input. In my case, all of the blocks are identical (viz., they are the tribanded matrix, B[1,-2,1]), and I want to place N-1 of these blocks on the diagonal of the larger matrix. Obviously, I'm not going to manually type in the block N-1 times, so I was hoping that maybe someone out there would have a clever solution to this problem. If there are other ways of creating the matrix I'm looking for, that's great too, but it would be neat if I could get this particular method to work. I'm rather new to MATLAB so forgive me if this seems like a dumb question.