Frequencies for first 10,000 rows of ivcontrast variable in nhamcsed2013 dataset :

Intravenous |
   contrast |      Freq.     Percent        Cum.
------------+-----------------------------------
         No |      9,953       99.53       99.53
        Yes |         47        0.47      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 7 Nov 2016