Frequencies for first 10,000 rows of pregnant variable in nhamcsopd1997 dataset :

 if female, |
 is patient |
  pregnant? |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |      1,082       10.82       10.82
          2 |      4,358       43.58       54.40
          3 |      1,064       10.64       65.04
          4 |      3,496       34.96      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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