[pymvpa] making new dataset from NiftiDataset

[Yaroslav Halchenko]

there are few ways to remapping of the labels... 

1. if you used  literal labels originally (e.g. ['cond1', 'cond2', 'reset']
then you could as well provide labels_map={'cond1':1, 'cond2':1,
'rest':2} to the NiftiDataset constructor

2. just remember original labels somewhere
 labels_all = ds.labels

and then remap them within the same dataset
 remapping = {1:2, 2:1, 3:1} # if original were 1 for rest, 2,3 for conditions
 ds.labels = [remapping[l] for l in ds.labels]

and then do that 'categories from rest' searchlight

or am I missing the point?

On Sun, 10 May 2009, Annalies wrote:

>    Hi,
>    I've run searchlight on a Nifti dataset using nu-SVM classifier and an
>    odd-even splitter. Now I'd like to use searchlight to see which voxels
>    do best at telling the samples from 2 categories from the rest. How do
>    I do this?
>    What I've tried: I've made a new dataset with label 1 for the two
>    categories I'm interested in and 2 for all the other non-rest samples,
>    but then I lose the mapping information searchlight needs. If I select
>    samples to run the searchlight on, it will try to tell apart all the
>    categories instead of just trying to distinguist categories 1 and 4
>    from the others. The only way I've come up with to do this is to create
>    a new numlabels file, but this is tedious and prone to error.  Is there
>    a better way?
>    Best,
>    Annalies

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