Hi - yes this should do what you want. On 9 Feb 2012, at 22:13, Rao, Anil W wrote: > Hi all. > > I am trying to generate 2 sets of 50 images, where each set is taken from a multivariate normal distribution with identity covariance matrix of size pxp, where p is the number of voxels in one of the images. > > Is this possible using randn? I tried doing this by creating 100 all zero images, merging them with -t option into a 4D image 'mzeros' and then did > > fslmaths mzeros -randn mrand > fslsplit mrand rand > > > I then take images rand00...rand49 images to be one set, and images rand50..rand99 the other, which *appears* reasonable, but will this give me precisely a sample of the correct distribution for each set? I am unsure how the randn function works... > > > Cheers > Anil --------------------------------------------------------------------------- Stephen M. Smith, Professor of Biomedical Engineering Associate Director, Oxford University FMRIB Centre FMRIB, JR Hospital, Headington, Oxford OX3 9DU, UK +44 (0) 1865 222726 (fax 222717) [log in to unmask] http://www.fmrib.ox.ac.uk/~steve ---------------------------------------------------------------------------