Frequencies for first 10,000 rows of drug_det variable in person dataset :

       DRUG |
DETERMAINAT |
        ION |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |         43        0.43        0.43
          2 |         10        0.10        0.53
          3 |          9        0.09        0.62
          7 |         35        0.35        0.97
          8 |      9,903       99.03      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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