Frequencies for first 10,000 rows of lmpmon variable in natl1975 dataset : Month Last | Normal | Menses | Began | Freq. Percent Cum. ------------+----------------------------------- 88 | 10,000 100.00 100.00 ------------+----------------------------------- Total | 10,000 100.00 by Jean Roth , jroth@nber.org , 3 Jan 2016