Frequencies for first 10,000 rows of mammo variable in nhamcsopd2010 dataset :

mammography |      Freq.     Percent        Cum.
------------+-----------------------------------
         no |      9,780       97.80       97.80
        yes |        220        2.20      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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