Jill,

You could use 3dTstat to average (etc.) across columns. Most AFNI programs of the '3d' vintage treat .1D files as datasets, with each column being a different sub-brick and each row being a different voxel. So 3dTstat, which does statistics across sub-bricks in each voxel, should do what you want. For example:

3dTstat -mean -prefix jed fred.1D'{5..9}[3..8]'

will average columns #3..8 together, for rows #5..9, and output 'jed.1D'. Note well that column and row indexes herein start at 0, as is usual in AFNI-land. If you want to pipe the output .1D file to stdout, use '-' for the prefix.

Most people don't know that .1D files can take row selectors in '{curly braces}', as well as column selectors in '[square brackets]'. Now you know. Use this new power wisely, and only for good.