Frequencies for first 10,000 rows of mammo variable in nhamcsopd2007 dataset :

mammography |      Freq.     Percent        Cum.
------------+-----------------------------------
         no |      9,765       97.65       97.65
        yes |        235        2.35      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 28 Mar 2016