Frequencies for first 10,000 rows of arrive variable in nhamcsed2007 dataset :

              mode of arrival |      Freq.     Percent        Cum.
------------------------------+-----------------------------------
                        blank |        249        2.49        2.49
                      unknown |        340        3.40        5.89
                    ambulance |      1,708       17.08       22.97
public service (nonambulance) |        261        2.61       25.58
      personal transportation |      7,442       74.42      100.00
------------------------------+-----------------------------------
                        Total |     10,000      100.00

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