Frequencies for a1 variable in midrvacc dataset :

         a1 |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |        292       62.93       62.93
          1 |          1        0.22       63.15
          2 |          5        1.08       64.22
          3 |          3        0.65       64.87
          4 |          5        1.08       65.95
          5 |          1        0.22       66.16
          6 |          1        0.22       66.38
          7 |          4        0.86       67.24
          8 |          7        1.51       68.75
          9 |          5        1.08       69.83
         10 |          5        1.08       70.91
         11 |          9        1.94       72.84
         12 |          8        1.72       74.57
         13 |          5        1.08       75.65
         14 |         10        2.16       77.80
         15 |         12        2.59       80.39
         16 |         10        2.16       82.54
         17 |          7        1.51       84.05
         18 |          6        1.29       85.34
         19 |         12        2.59       87.93
         20 |          7        1.51       89.44
         21 |          5        1.08       90.52
         22 |          9        1.94       92.46
         23 |          5        1.08       93.53
         24 |          2        0.43       93.97
         25 |          4        0.86       94.83
         26 |          4        0.86       95.69
         27 |          3        0.65       96.34
         28 |          6        1.29       97.63
         29 |          3        0.65       98.28
         30 |          1        0.22       98.49
         31 |          3        0.65       99.14
         32 |          1        0.22       99.35
         34 |          1        0.22       99.57
         36 |          1        0.22       99.78
         39 |          1        0.22      100.00
------------+-----------------------------------
      Total |        464      100.00

by Jean Roth , jroth@nber.org , 18 Apr 2016