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

  Hazardous |
  Materials |
Involvement |
/Placard-HM |
 5 Released |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,974       99.74       99.74
          1 |         13        0.13       99.87
          2 |         11        0.11       99.98
          8 |          2        0.02      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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