Davis <- read.table('http://math.uttyler.edu/nathan/classes/grad-statistics/data/davis.data',header=TRUE)

Cathedrals <- read.table('http://math.uttyler.edu/nathan/classes/grad-statistics/data/cathedral.data',header=TRUE)

Cathedrals[1:10,]

attach(Cathedrals)
goth <- ifelse(style=='g',1,0)

goth

mod.1 <- lm(y ~ x + style + x*style)
summary(mod.1)$coeff

mod.2 <- lm(y ~ x + style)
summary(mod.2)$coeff

mod.3 <- lm(weight ~ repwt + sex + repwt*sex)
summary(mod.3)

plot(repwt,weight,type='n')
points(repwt[sex=='F'],weight[sex=='F'],col='pink')
points(repwt[sex=='M'],weight[sex=='M'],col='blue')

mod.4 <- lm(weight ~ repwt + sex)
summary(mod.4)

mod.5 <- lm(weight ~ repwt)
summary(mod.5)

confint(mod.5)

Davis.1 <- Davis
Davis[12,]
Davis.1[12,2] <- 57
Davis.1[12,3] <- 166
Davis.1[12,]

mod.6 <- lm(weight ~ repwt + sex + repwt*sex,data=Davis.1)
summary(mod.6)
mod.7 <- lm(weight ~ repwt + sex,data=Davis.1)
summary(mod.7)
mod.8 <- lm(weight ~ repwt,data=Davis.1)
summary(mod.8)
confint(mod.8)