Frequencies for first 10,000 rows of retreffu variable in nhamcsed2010 dataset :

Return/refe |
       r to |
physician/c |
  linic for |
         FU |      Freq.     Percent        Cum.
------------+-----------------------------------
         no |      3,694       36.94       36.94
        yes |      6,306       63.06      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 28 Mar 2016