Frequencies for first 10,000 rows of ab_seiz variable in natl2015 dataset :

 Seizures Y |
        Yes |      Freq.     Percent        Cum.
------------+-----------------------------------
          N |      9,889       98.89       98.89
          U |        106        1.06       99.95
          Y |          5        0.05      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 20 Oct 2016