Frequencies for first 10,000 rows of mammog variable in h126f dataset :

 THIS VISIT |
 DID P HAVE |
A MAMMOGRAM |      Freq.     Percent        Cum.
------------+-----------------------------------
         -9 |        521        5.21        5.21
         -8 |         97        0.97        6.18
         -1 |         23        0.23        6.41
          1 |        514        5.14       11.55
          2 |      5,119       51.19       62.74
         95 |      3,726       37.26      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 27 Feb 2018