Homework4 - setwd("/Users/Bcollender/STAT 425") getwd()...

setwd("/Users/Bcollender/STAT 425")
getwd()
#question 1
Data1 <- read.table("advertspend.dat", header=TRUE)
Model1 <- lm(MILIMP~log(SPEND), data = Data1)
par(mfrow = c(2,2))
plot(Model1, add.smooth=FALSE)
library(MASS)
boxcox(Model1)
bcmod <- boxcox(Model1, plotit = FALSE)
bcmod$x[which.max(bcmod$y)]
#question 2
Data2 <- read.table("destroyers.dat", header = TRUE)
origModel2 <- lm(Displacement~Length+Beam+Draft, data = Data2)
Model2 <- lm(log(Displacement)~log(Length)+log(Beam)+log(Draft), data = Data2)
par(mfrow = c(2,2))
plot(Model2, add.smooth=FALSE)
summary(Model2)
point <- data.frame(Length=500, Beam = 69.5, Draft = 24)
predict(Model2, point, interval = "prediction")
exp(predict(Model2, point, interval = "prediction"))
confint(Model2)

#question 3
library(faraway)
help(seatpos)
Frwrd1 = lm(hipcenter~1, data = seatpos)
indep.vars <- ~Age + Weight + Ht + Leg
add1(Frwrd1, indep.vars, test = "F")
Frwrd1 = update(Frwrd1, .~. + Ht)
add1(Frwrd1, indep.vars, test = "F")
Bkwrd1 = lm(hipcenter ~ Age + Weight + Ht + Leg, data = seatpos)
drop1(Bkwrd1, test="F")
Bkwrd1 = update(Bkwrd1, .~. - Weight)
drop1(Bkwrd1, test="F")
Bkwrd1 = update(Bkwrd1, .~. - Age)
drop1(Bkwrd1, test="F")
Bkwrd1 = update(Bkwrd1, .~. - Leg)
drop1(Bkwrd1, test="F")
library(leaps)
x = model.matrix(hipcenter~Age+Weight+Ht+Leg-1, data = seatpos)
y = seatpos$hipcenter
bestmods = leaps(x,y,nbest=1)
bestmods
Cpplot(bestmods)
colnames(x)[c(1,3,4)]

step(lm(hipcenter~1, data = seatpos), scope = ~Age + Weight + Ht + Leg, direction =
"both")