Frequencies for first 10,000 rows of xray variable in namcs2001 dataset :

      x-ray |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,385       93.85       93.85
          1 |        615        6.15      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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