Frequencies for first 10,000 rows of shipnum variable in natl1979 dataset :

   Shipment |
     number |      Freq.     Percent        Cum.
------------+-----------------------------------
         01 |      2,018       20.18       20.18
         02 |      4,358       43.58       63.76
         03 |      3,624       36.24      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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