Frequencies for first 10,000 rows of chromo variable in natl1991 dataset :

      Other |
chromosomal |
  anomalies |      Freq.     Percent        Cum.
------------+-----------------------------------
          2 |      9,991       99.91       99.91
          9 |          9        0.09      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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