Frequencies for first 10,000 rows of psa variable in namcs2015 dataset :

        PSA |
  (prostate |
   specific |
   antigen) |
       test |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,750       97.50       97.50
          1 |        250        2.50      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 25 Oct 2017