Frequencies for pmcycl_cy variable in parkwork dataset :

  Number of |
     Engine |
     Cycles |      Freq.     Percent        Cum.
------------+-----------------------------------
            |        993       99.10       99.10
          4 |          9        0.90      100.00
------------+-----------------------------------
      Total |      1,002      100.00

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