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

  Hazardous |
  Materials |
Involvement |
/Placard-HM |
  2 Placard |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,974       99.74       99.74
          1 |          1        0.01       99.75
          2 |         23        0.23       99.98
          8 |          2        0.02      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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