Frequencies for first 10,000 rows of pregnant variable in nhamcsopd2006 dataset :

 if female, is |
       patient |
     pregnant? |      Freq.     Percent        Cum.
---------------+-----------------------------------
           Yes |        885        8.85        8.85
            No |      4,286       42.86       51.71
       Unknown |        513        5.13       56.84
Not applicable |      3,896       38.96       95.80
         Blank |        420        4.20      100.00
---------------+-----------------------------------
         Total |     10,000      100.00

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