Frequencies for first 10,000 rows of lung variable in natlterr1994 dataset :

   Acute or |
    chronic |
       lung |
    disease |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |         53        0.53        0.53
          2 |      9,935       99.35       99.88
          9 |         12        0.12      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 22 Dec 2015