Frequencies for first 10,000 rows of extrxray variable in nhamcsed1993 dataset :

  extremity |
      x-ray |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      8,619       86.19       86.19
          1 |      1,381       13.81      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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