Frequencies for first 10,000 rows of pregnant variable in nhamcsed1997 dataset :

 if female, |
 is patient |
  pregnant? |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        236        2.36        2.36
          2 |      3,204       32.04       34.40
          3 |      1,764       17.64       52.04
          4 |      4,796       47.96      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 28 Mar 2016