Frequencies for first 10,000 rows of pregtest variable in nhamcsed1995 dataset : pregnancy | test | Freq. Percent Cum. ------------+----------------------------------- 0 | 9,730 97.30 97.30 1 | 270 2.70 100.00 ------------+----------------------------------- Total | 10,000 100.00 by Jean Roth , jroth@nber.org , 28 Mar 2016