Frequencies for first 10,000 rows of ip_syph variable in natl2014 dataset :

 Syphilis Y |
        Yes |      Freq.     Percent        Cum.
------------+-----------------------------------
          N |      9,826       98.26       98.26
          U |        169        1.69       99.95
          Y |          5        0.05      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 15 Jun 2016