Frequencies for first 10,000 rows of telephon variable in nhamcsopd1993 dataset : telephone | follow-up | planned | Freq. Percent Cum. ------------+----------------------------------- 0 | 9,643 96.43 96.43 1 | 357 3.57 100.00 ------------+----------------------------------- Total | 10,000 100.00 by Jean Roth , jroth@nber.org , 28 Mar 2016