Frequencies for first 10,000 rows of drl_t variable in vindecode dataset : (daytime | running | lights) | description | Freq. Percent Cum. --------------+----------------------------------- | 2,865 28.65 28.65 Not Available | 2,839 28.39 57.04 Optional | 1,228 12.28 69.32 STANDARD | 2 0.02 69.34 Standard | 2,781 27.81 97.15 Unknown | 285 2.85 100.00 --------------+----------------------------------- Total | 10,000 100.00 by Jean Roth , jroth@nber.org , 22 Oct 2016