Frequencies for first 10,000 rows of xray variable in nhamcsopd2001 dataset :

      x-ray |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,436       94.36       94.36
          1 |        564        5.64      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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