Frequencies for first 10,000 rows of mricontrast variable in nhamcsed2014 dataset :

    Was MRI |
ordered/pro |
 vided with |
intravenous |
       (IV) |
   contrast |      Freq.     Percent        Cum.
------------+-----------------------------------
      Blank |      9,915       99.15       99.15
    Unknown |         22        0.22       99.37
        Yes |         17        0.17       99.54
         No |         46        0.46      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 11 Apr 2017