Frequencies for first 10,000 rows of totamb variable in nhamcsopd1998 dataset :

     total # of ambulatory surgical |
                         procedures |      Freq.     Percent        Cum.
------------------------------------+-----------------------------------
                                  0 |      9,511       95.11       95.11
                                  1 |        448        4.48       99.59
                                  2 |         41        0.41      100.00
------------------------------------+-----------------------------------
                              Total |     10,000      100.00

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