15.18  DATA 

     DATA [SET] [NAME="name"] This starts a new data set.  If the data is
broken up into sets, you may specify which data set to plot.  Also JOIN
and HISTOGRAM will plot each set independently.  The Data sets are
numbered in order 1,2,3...  When a data set is deleted the remaining data
sets are renumbered.  You may specify data sets either by number or name.

You may intermix MESH and regular data sets.