It turns out the (relatively) hard work was just adapting the data editor spreadsheet for matrix use (still not as good as it could be, but workable) and hooking up a matrix back-end. That done, a lot of other things come more or less for free. So here's what we have now: * A "properties" window for matrices. Not very interesting for non-square matrices at this point, but for square ones you get a reading on symmetry, positive definiteness, determinant, eigenvalues and so on. * The gui matrix editor now has a menu of transformations such as X'X, transpose, Cholesky decomposition and such. Also a "save as" button to let you save a transformation under another name. Might be of some use for pedagogical purposes. Allin.