Frequencies for first 10,000 rows of chromo variable in natlterr2001 dataset :

      Other |
chromosomal |
  anomalies |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |          3        0.03        0.03
          2 |      9,971       99.71       99.74
          8 |         20        0.20       99.94
          9 |          6        0.06      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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