Frequencies for first 10,000 rows of monitor variable in linkco1991us_num dataset :

 Electronic |
      fetal |
 monitoring |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |      6,050       60.50       60.50
          2 |      3,739       37.39       97.89
          9 |        211        2.11      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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