system.time(A <-read.table(file="airline100M.csv", sep=",", header=T, nrows=100000000,colClasses=c(rep("NULL",3), "factor", rep("NULL", 10), "numeric", "numeric", rep("NULL", 13)))) gc(T) system.time(result <- lm(ArrDelay ~ DepDelay + DayOfWeek, data = A)) gc(T) Sys.time()