Frequencies for first 10,000 rows of glaucoma variable in namcs1997 dataset :

   glaucoma |
       exam |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,690       96.90       96.90
          1 |        310        3.10      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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