Frequencies for ptrailer variable in parkwork dataset :

    vehicle |
   trailing |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      1,040       90.75       90.75
          1 |         99        8.64       99.39
          2 |          1        0.09       99.48
          5 |          1        0.09       99.56
          9 |          5        0.44      100.00
------------+-----------------------------------
      Total |      1,146      100.00

by Jean Roth , jroth@nber.org , 22 Oct 2016