Frequencies for first 10,000 rows of hyaline variable in natlterr2001 dataset :

    Hyaline |
   membrane |
    disease |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |         19        0.19        0.19
          2 |      9,957       99.57       99.76
          8 |         20        0.20       99.96
          9 |          4        0.04      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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