The subgroup summary statistics are classified into groups according to the levels of the symbol-variable and are identified on the chart with unique plotting symbols. If you use a graphics device, ...

title 'Individual Measurements Chart and Box-and-Whisker Plot'; symbol v=dot c=yellow; proc shewhart data=engines; irchart weight*id / ltmplot = schematic ltmargin = 8 nochart2 cframe = vigb cconnect ...