2015-08-23 02:59:23 +0100 received badge ● Famous Question (source) 2014-04-14 10:47:45 +0100 received badge ● Notable Question (source) 2013-08-12 00:36:46 +0100 received badge ● Popular Question (source) 2012-08-29 12:12:21 +0100 received badge ● Student (source) 2012-08-29 01:18:04 +0100 marked best answer Generating random normal vectors and matrices From within Sage, I'd probably do something like sage: m = Matrix(RR, 3, lambda i,j: normalvariate(0, 1)) sage: m [ -2.62449138547238 0.892440016295533 0.370843911194638] [-0.556296861517236 0.298136996038704 0.244309907008598] [ -1.48878357104797 0.424470381797098 -1.02406746759107]  for the first. (See also numpy.random.normal, although you'd have to feed it into a Matrix to get the full Sage functionality anyway.) For the second, the best way would depend upon whether you want to specify an exact number of non-zero terms or only an approximate fraction. If exact, then maybe just use sample to decide which terms you want to be nonzero and use the dict constructor: sage: sample(xrange(10), 3) [8, 1, 6] sage: {index: normalvariate(0, 1) for index in sample(xrange(10), 3)} {0: 0.6312570531236461, 1: -0.3442153313732221, 7: 0.12271841036659839} sage: vector(RR, 10, {index: normalvariate(0, 1) for index in sample(xrange(10), 3)}) (0.000000000000000, 0.000000000000000, 0.000000000000000, -2.16336854587694, -0.123030170562214, 0.000000000000000, 0.000000000000000, -1.99437183544239, 0.000000000000000, 0.000000000000000)  [Note that since I'm computing new random numbers each time, the three lines above aren't consistent with each other. But you should get the idea.] 2012-08-29 01:18:04 +0100 received badge ● Scholar (source) 2012-08-29 00:53:10 +0100 commented answer Generating random normal vectors and matrices Thanks for these suggestions. 2012-08-29 00:52:39 +0100 received badge ● Supporter (source) 2012-08-28 22:29:21 +0100 asked a question Generating random normal vectors and matrices I'm new to sage, and am looking for the best ways to generate matrices and vectors with the following properties: Matrices with independent normal entries. The default distribution of entries in matrices generated by random_matrix seems to be uniform over [-1,1]. Can that be changed? Random (normal) vectors with fixed sparsity, in the sense that only a given number of the entries are non-zero. Thanks for any assistance.