Frequencies for first 10,000 rows of mriunk variable in nhamcsed2007 dataset :

 mri - site |
        not |
  specified |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,986       99.86       99.86
          1 |         14        0.14      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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