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 |      9,979       99.79       99.79
          1 |          2        0.02       99.81
          2 |          3        0.03       99.84
          3 |         14        0.14       99.98
         88 |          2        0.02      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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