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

     Driver |
   Presence |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |      9,842       98.42       98.42
          2 |         81        0.81       99.23
          3 |         39        0.39       99.62
          9 |         38        0.38      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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