[pymvpa] Found the problem (hopefully): suspicious results

[Yaroslav Halchenko]

On Wed, 02 Mar 2011, Nynke van der Laan wrote:
> dataset.map2Nifti(sl_map).save('filename.nii.gz'). When I open this
> nifti in MRIcron than the distribution suddenly is totally different
> (as I reported earlier: the histogram with a peak at 0.6).

could be effect of having scl_slope (e.g. = 1.2) defined in the original nifti and
propagated into the saved map, which had values with peak at 0.5.  Since
MRIcron probably takes care about scaling data appropriately -- 0.5
would become 0.6.

Please inspect nifti header of both files for scl_slope values with the
tool of your preference.  or within PyMVPA

print dataset.niftihdr['scl_slope']
print dataset.map2Nifti(dataset.samples).header['scl_slope']


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