Using Workbench Command

AVERAGE CIFTI ROWS ACROSS SUBJECTS BY ROI
   wb_command -cifti-average-dense-roi
      <cifti-out> - output - output cifti dscalar file

      [-cifti-roi] - cifti file containing combined weights
         <roi-cifti> - the roi cifti file

         [-in-memory] - cache the roi in memory so that it isn't re-read for
            each input cifti

      [-left-roi] - weights to use for left hempsphere
         <roi-metric> - the left roi as a metric file

      [-right-roi] - weights to use for right hempsphere
         <roi-metric> - the right roi as a metric file

      [-cerebellum-roi] - weights to use for cerebellum surface
         <roi-metric> - the cerebellum roi as a metric file

      [-vol-roi] - voxel weights to use
         <roi-vol> - the roi volume file

      [-left-area-surf] - specify the left surface for vertex area correction
         <left-surf> - the left surface file

      [-right-area-surf] - specify the right surface for vertex area correction
         <right-surf> - the right surface file

      [-cerebellum-area-surf] - specify the cerebellum surface for vertex area
         correction
         <cerebellum-surf> - the cerebellum surface file

      [-cifti] - repeatable - specify an input cifti file
         <cifti-in> - a cifti file to average across

      Averages rows for each map of the ROI(s), across all files.  ROI maps are
      treated as weighting functions, including negative values.  For
      efficiency, ensure that everything that is not intended to be used is
      zero in the ROI map.  If -cifti-roi is specified, -left-roi, -right-roi,
      -cerebellum-roi, and -vol-roi must not be specified.  If multiple
      non-cifti ROI files are specified, they must have the same number of
      columns.