Frequencies for first 10,000 rows of xray variable in nhamcsopd1999 dataset :

      x-ray |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,268       92.68       92.68
          1 |        732        7.32      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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