Frequencies for first 10,000 rows of urf_card variable in natl2005 dataset :

  Cardiac U |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |         23        0.23        0.23
          2 |      9,854       98.54       98.77
          9 |        123        1.23      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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