Frequencies for first 10,000 rows of xray variable in nhamcsopd2000 dataset :

      x-ray |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,333       93.33       93.33
          1 |        667        6.67      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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