Frequencies for first 10,000 rows of vmonth variable in nhamcsopd1997 dataset :

   month of |
      visit |      Freq.     Percent        Cum.
------------+-----------------------------------
    January |      1,015       10.15       10.15
   February |        937        9.37       19.52
      March |        945        9.45       28.97
      April |        840        8.40       37.37
        May |        501        5.01       42.38
       June |      1,012       10.12       52.50
       July |      1,081       10.81       63.31
     August |        508        5.08       68.39
  September |        640        6.40       74.79
    October |        853        8.53       83.32
   November |        765        7.65       90.97
   December |        903        9.03      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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