Frequencies for first 10,000 rows of uop_ultra variable in natl2005 dataset :

 Ultrasound |
          U |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |      5,288       52.88       52.88
          2 |      4,604       46.04       98.92
          9 |        108        1.08      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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