Frequencies for ptrailer variable in parkwork dataset :

    vehicle |
   trailing |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |        985       90.45       90.45
          1 |         96        8.82       99.27
          2 |          2        0.18       99.45
          3 |          1        0.09       99.54
          5 |          4        0.37       99.91
          9 |          1        0.09      100.00
------------+-----------------------------------
      Total |      1,089      100.00

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