function addlist (series y, list list0, list addlist)
    ols y list0 --quiet
    aic_min = $aic
    printf "Baseline        AIC = %g\n", aic_min
    loop while (nelem(addlist) > 0) --quiet
       string bestx = null
       # check each remaining additional regressor
       loop foreach i addlist --quiet
          ols y list0 addlist.$i --quiet
          aic = $aic
          if (aic < aic_min)
	     aic_min = aic
	     string bestx = "$i"
          endif
       endloop 
       if strlen(bestx)
          printf "Adding %-8s AIC = %g\n", @bestx, aic
          list list0 += addlist.@bestx
          list addlist -= addlist.@bestx
       else
          break
       endif
    endloop 
    printf "\nMinimized AIC = %g, with this model:\n", aic_min 
    ols y list0
end function

open data4-10
list list0 = 0
list list1 = 2 3 4 5 6 7 8 9
addlist(ENROLL, list0, list1)

# but compare...
ols ENROLL 0 CATHOL WHITE INCOME COLLEGE