Frequencies for first 10,000 rows of dr_pres variable in vehicle dataset :

     Driver |
   Presence |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |      9,918       99.18       99.18
          2 |         45        0.45       99.63
          9 |         37        0.37      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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