Frequencies for first 10,000 rows of vmonth variable in nhamcsopd1994 dataset :

   month of |
      visit |      Freq.     Percent        Cum.
------------+-----------------------------------
    January |        737        7.37        7.37
   February |        812        8.12       15.49
      March |        937        9.37       24.86
      April |      1,102       11.02       35.88
        May |        864        8.64       44.52
       June |        556        5.56       50.08
       July |        809        8.09       58.17
     August |        909        9.09       67.26
  September |        908        9.08       76.34
    October |        994        9.94       86.28
   November |        753        7.53       93.81
   December |        619        6.19      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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