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

      Other |
circulatory |
/respirator |
y anomalies |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |          6        0.06        0.06
          2 |      9,985       99.85       99.91
          9 |          9        0.09      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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