Frequencies for first 10,000 rows of xray variable in nhamcsopd1995 dataset :

      x-ray |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      8,976       89.76       89.76
          1 |      1,024       10.24      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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