Frequencies for first 10,000 rows of amb variable in nhamcsopd2000 dataset :

       were |
 ambulatory |
   surgical |
      procs |
 performed? |      Freq.     Percent        Cum.
------------+-----------------------------------
         No |      9,240       92.40       92.40
        Yes |        493        4.93       97.33
 Item blank |        267        2.67      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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