Frequencies for first 10,000 rows of prov1315 variable in pos1993 dataset :

 tech super |
          - |
cytogenetic |
          s |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,982       99.82       99.82
          1 |         12        0.12       99.94
          2 |          5        0.05       99.99
          3 |          1        0.01      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 26 Jan 2016