Frequencies for first 10,000 rows of mammo variable in nhamcsopd1999 dataset :

mammography |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,800       98.00       98.00
          1 |        200        2.00      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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