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

  hazardous |
  materials |
involvement |
/placard-hm |
 5 released |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,979       99.79       99.79
          1 |         17        0.17       99.96
          2 |          2        0.02       99.98
          8 |          2        0.02      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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