Frequencies for first 10,000 rows of xray variable in nhamcsed2006 dataset :

      x-ray |      Freq.     Percent        Cum.
------------+-----------------------------------
         no |      6,691       66.91       66.91
        yes |      3,309       33.09      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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