Frequencies for first 10,000 rows of extrxray variable in nhamcsed1998 dataset :

  extremity |
      x-ray |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,042       90.42       90.42
          1 |        958        9.58      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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