mhampton wrote: > If you convert to numpy matrices, then Sage is pretty competitive with > matlab. We still have some room for improvement in making it easy > though - despite Jason Grout's improvements, a matrix over RDF is > missing some methods I'd like, such as the singular value > decomposition. As an example, to extend one of Minh's examples to get > the smallest singular value of a bunch of matrices you'd have to do > something like: > > sage: rand_row = lambda n: [randint(1, 10) for i in xrange(n)] > sage: rand_mat = lambda nrows, ncols: [rand_row(ncols) for i in xrange > (nrows)] > sage: rows = [randint(1, 10) for i in xrange(10)] > sage: cols = [randint(1, 10) for i in xrange(10)] > sage: M = map(rand_mat, rows, cols) > sage: M = map(matrix, M) > > sage: from numpy.linalg import svd > sage: smallest_singular_values = lambda x: min(svd(x.numpy())[1]) > sage: ssvM = map(smallest_singular_values,M) > > Or perhaps I'm missing something and that import isn't necessary.
Use .SVD(): sage: a=random_matrix(RDF,4) sage: a [-0.0589149680447 -0.171553538689 0.0504191493106 -0.728358759815] [ 0.939727693257 -0.367536042534 -0.721360348176 0.0692413755066] [ -0.265450259774 -0.0414843551839 0.329102195484 -0.152151468706] [ 0.166692127509 -0.107846656469 -0.964097402323 -0.752787313591] sage: a.SVD() ( [ 0.136357448911 0.618194289876 0.67734122822 -0.374768363984] [ 0.678366688256 -0.550596271759 0.457486597867 0.165433958308] [-0.204023508917 0.263478231509 0.295912033247 0.895203718664] [ 0.692531364055 0.495236092193 -0.494318664329 0.175472450502], [ 1.59046610372 0.0 0.0 0.0] [ 0.0 1.05246085825 0.0 0.0] [ 0.0 0.0 0.455098193519 0.0] [ 0.0 0.0 0.0 0.064329905844], [ 0.502396175818 -0.514242277172 0.503316286102 -0.479401375714] [-0.213107477417 0.0303771634211 -0.534627925294 -0.81721197526] [-0.765363106349 0.0357282483633 0.611065745739 -0.198850351] [-0.341178254043 -0.85636183975 -0.295709911949 0.250594186611] ) sage: What apparently is missing is that matrix/matrix_double_dense.pyx has not been converted to rest yet, so the SVD function does not show up in the reference manual. Thanks, Jason -- To post to this group, send an email to sage-devel@googlegroups.com To unsubscribe from this group, send an email to sage-devel+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URL: http://www.sagemath.org
