Frequencies for first 10,000 rows of lumbpunc variable in nhamcsed2000 dataset :

     lumbar |
   puncture |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,980       99.80       99.80
          1 |         20        0.20      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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