Frequencies for first 10,000 rows of retreffu variable in nhamcsed2013 dataset :

Return/refe |
       r to |
physician/c |
  linic for |
         FU |      Freq.     Percent        Cum.
------------+-----------------------------------
         No |      3,437       34.37       34.37
        Yes |      6,563       65.63      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 7 Nov 2016