Frequencies for first 10,000 rows of ivcontrast variable in nhamcsed2012 dataset :

Intravenous |
   contrast |      Freq.     Percent        Cum.
------------+-----------------------------------
         No |      9,967       99.67       99.67
        Yes |         33        0.33      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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