Frequencies for first 10,000 rows of xray variable in nhamcsopd2005 dataset :

      x-ray |      Freq.     Percent        Cum.
------------+-----------------------------------
         no |      9,067       90.67       90.67
        yes |        933        9.33      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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