Frequencies for first 10,000 rows of uop_ultra variable in natl2003 dataset :

 Ultrasound |
          U |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |      5,407       54.07       54.07
          2 |      3,825       38.25       92.32
          8 |          7        0.07       92.39
          9 |        761        7.61      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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