Frequencies for first 10,000 rows of xray variable in nhamcsed2009 dataset :

      x-ray |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      6,571       65.71       65.71
          1 |      3,429       34.29      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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