Frequencies for ptrailer variable in parkwork dataset :

    Vehicle |
   Trailing |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |        965       90.70       90.70
          1 |         89        8.36       99.06
          2 |          3        0.28       99.34
          5 |          1        0.09       99.44
          9 |          6        0.56      100.00
------------+-----------------------------------
      Total |      1,064      100.00

by Jean Roth , jroth@nber.org , 18 Apr 2016