¥Conjunction Junction: WhatÕs Your Function?
HThe program 3dcalc is a general purpose program for performing logic and arithmetic calculations
åcommand line is of the format
å3dcalc -a Dset1 -b Dset2 ... -expr (a * b...)
å some expressions can be used to select voxels with values v meeting certain criteria:
ífind voxels where v > th and mark them with value=1
ístep (v Ð th)  
íin a range of values: thmin < v < thmax
ístep (v Ð thmin) * step (thmax - v)
íexact value: v = n
í 1 Ð bool(v Ð n) 
åcreate masks to apply to functional datasets
ítwo values both above threshold:
ístep(v-A)*step(w-B)