Frequencies for first 10,000 rows of chromo variable in natl1993 dataset :

      Other |
chromosomal |
  anomalies |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |          3        0.03        0.03
          2 |      9,997       99.97      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 22 Dec 2015