advt<-c(2,3,4,5,6)
sales<-c(4,4,6,6,10)
data<-data.frame(advt,sales)

ols<-lm(sales~advt)
summary(ols)

library(stargazer)
stargazer(ols,type="text")

predict(lm(sales~advt))
new.advt<-data.frame(advt = 7)
predict(ols, newdata=new.advt)
predict(ols, newdata=new.advt, interval = "confidence")
predict(ols, newdata=new.advt, interval = "prediction")

pred.int <- predict(ols, interval = "prediction")
mydata <- cbind(data, pred.int)

library("ggplot2")
p <- ggplot(mydata, aes(advt, sales)) +
  geom_point() +
  stat_smooth(method = lm)
p + geom_line(aes(y = lwr), color = "red", linetype = "dashed")+
  geom_line(aes(y = upr), color = "red", linetype = "dashed")