Frequencies for first 10,000 rows of extrxray variable in nhamcsed1997 dataset :

  extremity |
      x-ray |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      8,956       89.56       89.56
          1 |      1,044       10.44      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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