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¥Conjunction Junction: WhatÕs Your Function?
HThe program 3dcalc is a general purpose program for performing logic and arithmetic calculations
å Command line is of the format
å3dcalc -a Dset1 -b Dset2 ... -expr Ò(a * b ...)Ó
å
å
å Some expressions can be used to select voxels with values v meeting certain criteria:
íFind voxels where v ³ th and mark them with value=1
í    expression =   step (v Ð th)   (result is 1 or 0)
íIn a range of values: thmin ² v ² thmax
í    expression =   step (v Ð thmin) * step (thmax - v)
íExact value: v = n
í     expression =   equals(v Ð n)  
å Create masks to apply to functional datasets
íTwo values both above threshold (e.g., active in both tasks; ÒconjunctionÓ)
í    expression =   step(v-A)*step(w-B)
values from Dset1 are
to be called ÔaÕ in -expr
mathematical expression
combining input dataset values