Hi Lydia,
The difference between the results of the 3dfractionize and the
3dresample commands is small. The 3dfractionize program uses a
counting method to determine which input voxel's value to copy
to the corresponding output voxel (the one with the highest
occupancy).
The 3dresample program uses one of the various interpolation
methods (nearest neighbor, linear, cubic, blocky) to resample
the data.
So the two programs will typically produce slightly different
results, but will end up being very close. It just depends upon
the way you want to resample your data.
- rick