Frequencies for first 10,000 rows of refphys variable in nhamcsed1993 dataset :

  return to |
  referring |
  physician |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      8,195       81.95       81.95
          1 |      1,805       18.05      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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