Hi Mithun,

You can use the '-1clust_order' option with 3dclust to get a
list of clusters, sorted by volume of cluster. Note that the
options is actually explained in '3dmerge -help', but also
applies to 3dclust.

This dataset can be used as the mask dataset with 3dmaskave
to output the average (etc.) of values over a mask. The
3dmaskdump program will output the individual values of a
dataset (over a mask), which does not seem to be what you
want, unless you want to then import them into excel, or
something like that.

But it seems like 3dmaskave should do what you are looking
to do.

- rick