Frequencies for first 10,000 rows of centline variable in nhamcsed2009 dataset :

    central |
       line |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,988       99.88       99.88
          1 |         12        0.12      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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