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

  Hazardous |
  Materials |
Involvement |
/Placard-HM |
 5 Released |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,984       99.84       99.84
          1 |         10        0.10       99.94
          2 |          3        0.03       99.97
          8 |          3        0.03      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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