Frequencies for first 10,000 rows of chromo variable in linkco1991us_num dataset :

      Other |
chromosomal |
  anomalies |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        136        1.36        1.36
          2 |      9,591       95.91       97.27
          9 |        273        2.73      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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