ncol(cars);nrow(cars)
dim(cars)
lm(dist~speed,data=cars)
cars$qspeed=cut(cars$speed,breaks=quantile(cars$speed),include.lowest=TRUE)
names(cars)
cars[3]
cars[,3]
table(cars[3])
is.factor(cars$qspeed)
plot(dist~qspeed,data=cars)
(a=lm(dist~qspeed,data=cars))
summary(a)