Frequencies for first 10,000 rows of refer variable in nhamcsopd1996 dataset :

    was pat |
referred by |
        oth |
  physician |
 for visit? |      Freq.     Percent        Cum.
------------+-----------------------------------
        Yes |      2,443       24.43       24.43
         No |      7,557       75.57      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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