data(cars)
carfit <- lm(dist ~ speed, data=cars)
summary(carfit)
plot(speed ~ dist, data=cars)
abline(carfit)
vcov <- summary(carfit)$sigma^2 * summary(carfit)$cov.unscaled
carfitunres <- lm(dist ~ speed + I(speed^2), data=cars)
carfitres <- lm(dist ~ speed, data=cars)
anova(carfitres,carfitunres)
library(lmtest)
bptest(carfit)
dwtest(carfit)
carpred <- predict(carfit,se.fit=TRUE,interval="prediction")
carpred$fit[1,]