Frequencies for first 10,000 rows of shipnum variable in natl1976 dataset :

   Shipment |
     number |      Freq.     Percent        Cum.
------------+-----------------------------------
         01 |      2,696       26.96       26.96
         02 |      4,256       42.56       69.52
         03 |      3,048       30.48      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 3 Jan 2016