Frequencies for first 10,000 rows of uop_ultra variable in natlterr2003 dataset :

 Ultrasound |
          U |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |      4,405       44.05       44.05
          2 |      5,572       55.72       99.77
          8 |         23        0.23      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 22 Dec 2015