Frequencies for first 10,000 rows of totamb variable in nhamcsopd1999 dataset :

     total # of ambulatory surgical |
                         procedures |      Freq.     Percent        Cum.
------------------------------------+-----------------------------------
                                  0 |      9,376       93.76       93.76
                                  1 |        532        5.32       99.08
                                  2 |         92        0.92      100.00
------------------------------------+-----------------------------------
                              Total |     10,000      100.00

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