On Thursday 08 January 2009 15:29:47 Dave Brohawn wrote:

> I would like to create a functional constraint including only the 25%
> most active voxels (top quartile).
>
> Is there a command that can achieve this?
>

You can use 'mris_calc' (the development version):

$>mris_calc someVolume.mgz stats

--> will dump min/max/mean/std data

Based on the range max-min determine the 25% threshold, then:

$>mris_calc -o top25pc.mgz someVolume.mgz gte <threshold>

--> top25pc.mgz will contain only the voxels in someVolume.mgz with intensities greater than or equal to <threshold>.

-=R

--
Rudolph Pienaar, M.Eng, D.Eng / email: rudolph@nmr.mgh.harvard.edu
MGH/MIT/HMS Athinoula A. Martinos Center for Biomedical Imaging
149 (2301) 13th Street, Charlestown, MA 02129 USA