Frequencies for first 10,000 rows of rh variable in natl1990 dataset :

         Rh |
sensitizati |
         on |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |         52        0.52        0.52
          2 |      9,899       98.99       99.51
          8 |          1        0.01       99.52
          9 |         48        0.48      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 3 Jan 2016