Frequencies for first 10,000 rows of psa variable in nhamcsopd1995 dataset :

   psa test |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,970       99.70       99.70
          1 |         30        0.30      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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