Frequencies for first 10,000 rows of psa variable in nhamcsopd1998 dataset :

   psa test |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,954       99.54       99.54
          1 |         46        0.46      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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