Frequencies for first 10,000 rows of mm_mtr variable in natlterr2012 dataset :

   Maternal |
Transfusion |
622=f_mm_mt |
     rans R |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      1,163       11.63       11.63
          N |      8,451       84.51       96.14
          U |        374        3.74       99.88
          Y |         12        0.12      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 5 May 2016