Frequencies for first 10,000 rows of monprec variable in natl1979 dataset :

     Detail |
      Month |
   Prenatal |
 Care began |      Freq.     Percent        Cum.
------------+-----------------------------------
          - |         85        0.85        0.85
          0 |        116        1.16        2.01
          1 |      1,085       10.85       12.86
          2 |      3,683       36.83       49.69
          3 |      2,191       21.91       71.60
          4 |      1,144       11.44       83.04
          5 |        682        6.82       89.86
          6 |        458        4.58       94.44
          7 |        320        3.20       97.64
          8 |        158        1.58       99.22
          9 |         78        0.78      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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