#part1
data(snowgeese)
attributes(snowgeese)
pairs(snowgeese)


#part2
fit1 = lm(photo~obs1, snowgeese)
summary(fit1)
par(mfrow=c(2,2))
plot(fit1)

#part3
fit2 = lm(sqrt(photo)~sqrt(obs1), snowgeese)
summary(fit2)
par(mfrow=c(2,2))
plot(fit2)

#part4
fit3 = lm(photo~obs1,weights=1/obs1, snowgeese)
summary(fit3)
par(mfrow=c(2,2))
plot(fit3)


#part5
snowgeese$avg = (snowgeese$obs1+snowgeese$obs2)/2
snowgeese$diff = (snowgeese$obs1-snowgeese$obs2)

fit4 = lm(photo~avg+diff,snowgeese)
summary(fit4)
par(mfrow=c(2,2))
plot(fit4)


fit6 = lm(photo~avg+diff, weights=1/avg, snowgeese)
summary(fit6)
plot(fit6)