Frequencies for s5_c4_6 variable in hcris2552_10_2012 dataset :

  number of |
   stations |
    s500000 |
00600 00400 |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |         14        0.22        0.22
          2 |          7        0.11        0.34
          3 |          5        0.08        0.42
          4 |          4        0.06        0.48
          6 |          1        0.02        0.50
         20 |          1        0.02        0.51
          . |      6,195       99.49      100.00
------------+-----------------------------------
      Total |      6,227      100.00

by Jean Roth , jroth@nber.org , 23 Aug 2018