Frequencies for first 10,000 rows of tono variable in namcs2012 dataset :

  Tonometry |      Freq.     Percent        Cum.
------------+-----------------------------------
         No |      9,941       99.41       99.41
        Yes |         59        0.59      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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