Frequencies for pmcycl_cy variable in parkwork dataset :

  number of |
     engine |
     cycles |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      1,085       99.45       99.45
          4 |          6        0.55      100.00
------------+-----------------------------------
      Total |      1,091      100.00

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