Usage: 3ddot [options] w dset
Output = linear prediction for w from 3dsvm
         - you can use sub-brick selectors on the dsets
         - the result is a number printed to stdout
  -mask mset   Means to use the dataset 'mset' as a mask:
                 Only voxels with nonzero values in 'mset'
                 will be averaged from 'dataset'.  Note
                 that the mask dataset and the input dataset
                 must have the same number of voxels.

This program accepts datasets that are modified on input according to the
following schemes:
  'r1+orig[3..5]'                                    {sub-brick selector}
  'r1+orig<100..200>'                                {sub-range selector}
  'r1+orig[3..5]<100..200>'                          {both selectors}
  '3dcalc( -a r1+orig -b r2+orig -expr 0.5*(a+b) )'  {calculation}
For the gruesome details, see the output of 'afni -help'.

++ Compile date = Sep 27 2020 {AFNI_20.2.19:linux_ubuntu_16_64}