house1=read.table("house1.txt")
names(house1)=c("price","assess","old","months")

pairs(house1)
attach(house1)

house1.lm=lm(price ~ assess + months)
summary(house1.lm)
anova(house1.lm)

anova(lm(price ~ months + assess))  # order matters in the ANOVA table
summary(lm(price~months))
anova(lm(price~months))

plot(assess,price)
lines(assess,fitted(house1.lm))    # this doesn't work very well
plot(assess,price)
lines(assess[order(assess)],fitted(house1.lm)[order(assess)])  # still weird

plot(fitted(house1.lm),resid(house1.lm))
plot(assess,resid(house1.lm))
plot(months,resid(house1.lm))
qqnorm(resid(house1.lm))

predict(house1.lm,data.frame(assess=80,months=6),interval="predict")



detach()
pairs(printlog)
attach(printlog)

print.lm2=lm(week3 ~ week1 + week2)
summary(print.lm2)           # interpret coefficients and p-values
anova(print.lm2)

plot(fitted(print.lm2),resid(print.lm2))   # not good
plot(week1,resid(print.lm2))
plot(week2,resid(print.lm2))
qqnorm(resid(print.lm2))      # how can we fix this?


print.lm3=lm(log(week3+1) ~ log(week1+1) + log(week2+1))
summary(print.lm3)
anova(print.lm3)

plot(fitted(print.lm3),resid(print.lm3))   # about as good as it will get here
qqnorm(resid(print.lm3))      

print.lm4=lm(sqrt(week3) ~ sqrt(week1) + sqrt(week2))
summary(print.lm4)                         # not as good as log
plot(fitted(print.lm4),resid(print.lm4))
qqnorm(resid(print.lm4))                   # not as good as log