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

  hazardous |
  materials |
involvement |
/placard-hm |
  2 placard |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,981       99.81       99.81
          1 |          1        0.01       99.82
          2 |         17        0.17       99.99
          8 |          1        0.01      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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