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

     Driver |
   Presence |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |      9,904       99.04       99.04
          2 |         50        0.50       99.54
          9 |         46        0.46      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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