Frequencies for first 10,000 rows of totamb variable in nhamcsopd1997 dataset :

     total # of ambulatory surgical |
                         procedures |      Freq.     Percent        Cum.
------------------------------------+-----------------------------------
                                  0 |      9,575       95.75       95.75
                                  1 |        385        3.85       99.60
                                  2 |         40        0.40      100.00
------------------------------------+-----------------------------------
                              Total |     10,000      100.00

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