Frequencies for first 10,000 rows of refer variable in nhamcsopd1992 dataset :

    Was pat |
referred by |
        oth |
  physician |
 for visit? |      Freq.     Percent        Cum.
------------+-----------------------------------
        Yes |      1,061       10.61       10.61
         No |      8,939       89.39      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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