Frequencies for first 10,000 rows of ifyes variable in nhamcsopd1993 dataset :

       if seen |
   before, for |
  condition in |
     item 11a? |      Freq.     Percent        Cum.
---------------+-----------------------------------
Not applicable |      2,319       23.19       23.19
           Yes |      6,056       60.56       83.75
            No |      1,625       16.25      100.00
---------------+-----------------------------------
         Total |     10,000      100.00

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