Frequencies for first 10,000 rows of prolong variable in natl1999 dataset :

  Prolonged |
      labor |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |         45        0.45        0.45
          2 |      9,955       99.55      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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