Frequencies for first 10,000 rows of ip_syph variable in natl2013 dataset :

   Syphilis |
596=f_ip_sy |
      ph) R |      Freq.     Percent        Cum.
------------+-----------------------------------
          N |      9,757       97.57       97.57
          U |        222        2.22       99.79
          Y |         21        0.21      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 22 Dec 2015