#montoria dia 17 de junho

install.packages('wooldridge')
library(wooldridge)

data("vote1")
vote1
attach(vote1)

model1 = lm(voteA~lexpendA+lexpendB+prtystrA)
summary(model1)

diff_exp = lexpendA - lexpendB
model2 = lm(voteA ~diff_exp+prtystrA)
summary(model2)

coeffs <- coefficients(model1)
model1$model
coeffs <- summary(model1)$coefficients
dim(coeffs)

(coeffs[2,1]+coeffs[3,1])/sqrt(coeffs[2,2]^2+coeffs[3,2]^2)

#chap3 C10
#i
data("htv")
attach(htv)
var(educ)
educ
fatheduc

sum(educ<=12)/length(educ)

sum(educ>12 & educ<=16)/length(educ)
mean(educ)
mean(fatheduc)

#ii
attach(htv)
model1 = lm(educ~motheduc+fatheduc)
summary(model1)

#iii
model2 = lm(educ~motheduc+fatheduc+abil)
summary(model2)


#iv
abil2 = abil^2
model3 = lm(educ~motheduc+fatheduc+abil+abil2)
summary(model3)


#v
coeffs <- summary(model3)$coefficients
f <- function(abil){
  y <- coeffs[1,1]+coeffs[2,1]*12.18+coeffs[3,1]*12.45+
    coeffs[4,1]*abil + coeffs[5,1]*abil^2
}
y <- f(abil)

plot(abil, y)

#chap 4 C11

#ii 
(coeffs[2,1]-coeffs[3,1])/sqrt(coeffs[2,2]^2+coeffs[3,2]^2)
pt(2.36,1230,lower.tail = FALSE)*2
pt(2.36,1230,lower.tail = FALSE)

#iii

model3 <- lm(educ~motheduc+fatheduc+abil+abil2+
               tuit17+tuit18)
summary(model3)  

linearHypothesis(model3, c("tuit17=0", 
                           "tuit18=0"))
#iv 
cor(tuit17,tuit18)

tuit1718 = (tuit17+tuit18)/2
model4 <- lm(educ~motheduc+fatheduc+abil+abil2+
               +tuit1718)
summary(model4)