[pymvpa] Nifti Datasets & Masking

James M. Hughes james.m.hughes at Dartmouth.EDU
Mon Jul 28 15:48:30 UTC 2008

Hi all,

Just a couple of questions for the more advanced users:

If I import a NiftiDataset that has a mask applied to it (from AFNI),  
does this mask persist when I import the data (using NiftiImage from  
the PyNifti package) and then NiftiDataset in PyMVPA?  How is masking  
actually achieved (i.e. are feature values set to 0 or are they  
excluded entirely)?  I'm a little concerned since this of course has  
direct bearing on RFE, etc., if it's not working with the right  
features to begin with (i.e. doesn't take a priori masking into  

Also, what is the easiest way to obtain the SVM weights used to rank  
features before elimination (i.e. the last snapshot of those weights  
when feature selection was finished)?  I'd like to be able to rank the  
voxels selected in order of their importance for determining the  
classification boundary.

Thanks for any insights --


More information about the Pkg-ExpPsy-PyMVPA mailing list