I would like to be able perform an operation on 4D files analogous to the dimensionality reduction operations that already exist, but It should calculate the mode. Ie. fslmaths 4D-image -Tmode 3D-modeimage should set each voxel to the most frequently encountered value along the time dimension. Ideally it would offer a choice for dealing with a multiple-solutions situation (random assignment, min value, max value). Perhaps this might be useful for other people, too? Thanks Rolf -- Rolf A Heckemann, MD PhD Médecin chercheur Fondation Neurodis CERMEP - Imagerie du Vivant Hôpital Neurologique Pierre Wertheimer 59 Boulevard Pinel 69003 Lyon France