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 |      9,981       99.81       99.81
          1 |          2        0.02       99.83
          2 |          2        0.02       99.85
          3 |          9        0.09       99.94
          4 |          1        0.01       99.95
          8 |          2        0.02       99.97
          9 |          1        0.01       99.98
         88 |          2        0.02      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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