Frequencies for first 10,000 rows of ab_seiz variable in natl2017 dataset :

 Seizures Y |
        Yes |      Freq.     Percent        Cum.
------------+-----------------------------------
          N |      9,919       99.19       99.19
          U |         72        0.72       99.91
          Y |          9        0.09      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 19 Sep 2018