Frequencies for ptrailer variable in parkwork dataset :

    vehicle |
   trailing |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      1,003       91.93       91.93
          1 |         81        7.42       99.36
          2 |          2        0.18       99.54
          4 |          1        0.09       99.63
          5 |          2        0.18       99.82
          9 |          2        0.18      100.00
------------+-----------------------------------
      Total |      1,091      100.00

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