Frequencies for first 10,000 rows of monprec variable in natl1976 dataset :

     Detail |
      Month |
   Prenatal |
 Care began |      Freq.     Percent        Cum.
------------+-----------------------------------
          - |         96        0.96        0.96
          0 |        122        1.22        2.18
          1 |        767        7.67        9.85
          2 |      3,679       36.79       46.64
          3 |      2,411       24.11       70.75
          4 |      1,237       12.37       83.12
          5 |        718        7.18       90.30
          6 |        431        4.31       94.61
          7 |        283        2.83       97.44
          8 |        193        1.93       99.37
          9 |         63        0.63      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 3 Jan 2016