library(alr3)
data(pipeline)
attributes(pipeline)

#===
#part1
plot(pipeline@Field, pipeline$Lab)

#===
#part2

fit1=(lm(Lab~Field, pipeline))
summary(fit1)

par(mfrow=c(2,2))
plot(fit1)

library(car)
ncv.test(fit1)



#===
#part3
ncv.test(fit1, ~pipeline$Field)

ncv.test(fit1, ~as.factor(pipeline$Batch))

fit2= lm(Lab~Field, weights = Field, pipeline)
summary(fit2)
fit3= lm(Lab~Field, weights = Batch, pipeline)
summary(fit3)

#====
#part4

ncv.test(fit1, ~pipeline$Field^2)