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

   month of |
      visit |      Freq.     Percent        Cum.
------------+-----------------------------------
    January |        747        7.47        7.47
   February |        909        9.09       16.56
      March |      1,221       12.21       28.77
      April |        763        7.63       36.40
        May |        712        7.12       43.52
       June |        951        9.51       53.03
       July |        634        6.34       59.37
     August |        770        7.70       67.07
  September |        563        5.63       72.70
    October |        850        8.50       81.20
   November |        852        8.52       89.72
   December |      1,028       10.28      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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