Frequencies for first 10,000 rows of pregnant variable in nhamcsopd1999 dataset :

 if female, |
 is patient |
  pregnant? |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |      1,073       10.73       10.73
          2 |      4,212       42.12       52.85
          3 |      1,114       11.14       63.99
          4 |      3,601       36.01      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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