Frequencies for first 10,000 rows of ab_surf variable in natlterr2008 dataset :

 Surfactant |
        RFP |
631=f_ab_su |
     rfac R |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      6,061       60.61       60.61
          N |      3,885       38.85       99.46
          Y |         54        0.54      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 3 May 2016