Frequencies for first 10,000 rows of spec variable in namcs1998 dataset :

  physician |
  specialty |      Freq.     Percent        Cum.
------------+-----------------------------------
        ADL |         40        0.40        0.40
         CD |         17        0.17        0.57
          D |         14        0.14        0.71
         FP |      3,200       32.00       32.71
        FPG |         20        0.20       32.91
         GE |         40        0.40       33.31
         GO |         18        0.18       33.49
         GP |        408        4.08       37.57
         GS |      1,182       11.82       49.39
         IM |      2,226       22.26       71.65
          N |         30        0.30       71.95
        NEP |          7        0.07       72.02
        OBG |        302        3.02       75.04
         OM |         15        0.15       75.19
        OPH |         67        0.67       75.86
        ORS |         84        0.84       76.70
          P |         25        0.25       76.95
         PD |      2,114       21.14       98.09
         PM |         31        0.31       98.40
         PN |         13        0.13       98.53
         PS |         14        0.14       98.67
        PUD |         84        0.84       99.51
        REN |         25        0.25       99.76
          U |         24        0.24      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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