Frequencies for first 10,000 rows of mri variable in nhamcsopd2009 dataset : mri | Freq. Percent Cum. ------------+----------------------------------- no | 9,803 98.03 98.03 yes | 197 1.97 100.00 ------------+----------------------------------- Total | 10,000 100.00 by Jean Roth , jroth@nber.org , 28 Mar 2016