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

  Hazardous |
  Materials |
Involvement |
/Placard-HM |
    4 Class |
     Number |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,984       99.84       99.84
          1 |          1        0.01       99.85
          2 |          4        0.04       99.89
          3 |          7        0.07       99.96
         88 |          4        0.04      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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