#Laboratorio 7

#Household-Income
Base = read.table(file.choose(), h=T, dec='.')
attach(Base)
names(Base)

par(mfrow = c(3,1))
plot(Y~X1) #X1: renta personal
abline(lm(Y~X1, data=Base), col=2)
plot(Y~X2) #X2: años de estudios
abline(lm(Y~X2, data=Base), col=2)
plot(Y~X3) #X3: tasa de desempleo
abline(lm(Y~X3, data=Base), col=2)

Mod01 = lm(Y~X1, data=Base)
Mod02 = lm(Y~X2, data=Base)
Mod03 = lm(Y~X3, data=Base)

#Seleccionamos modelo segun r^2
summary(Mod01)$adj.r.squared
summary(Mod02)$adj.r.squared
summary(Mod03)$adj.r.squared #Mayor r^2 entre los modelos

Mod04 = lm(Y~X1+X2, data=Base)
Mod05 = lm(Y~X2+X3, data=Base)
Mod06 = lm(Y~X3+X1, data=Base)

summary(Mod04)$adj.r.squared
summary(Mod05)$adj.r.squared
summary(Mod06)$adj.r.squared #r^2 aumenta

summary(Mod06)$coefficients

Mod07 = lm(Y~X1+X2+X3, data=Base)
summary(Mod07)$adj.r.squared #r^2 aumenta al incorporar X2
summary(Mod07)$coefficients

# ¿Que pasa si incorporamos una variable no correlacionada?
set.seed(123456)
Base$X4 = rnorm(50, mean=0, sd=1)

Mod08 = lm(Y~X1+X2+X3+X4, data=Base)
summary(Mod08)$adj.r.squared #r^2 disminuye al incorporar X4
summary(Mod08)$coefficients

# Parte 2

Algodon = read.table(file.choose(), header=TRUE, dec='.')
attach(Algodon)
head(Algodon)
names(Algodon)
par(mfrow = c(5,1))

plot(cottonq~quarter)
Mod01 = lm(cottonq~quarter)
summary(Mod01)$adj.r.squared
abline(Mod01, col=2)

plot(cottonq~year)
Mod02 = lm(cottonq~year)
summary(Mod02)$adj.r.squared
abline(Mod02, col=2)

plot(cottonq~whoprice)
Mod03 = lm(cottonq~whoprice)
summary(Mod03)$adj.r.squared #Mejor modelo
abline(Mod03, col=2)

plot(cottonq~impfab)
Mod04 = lm(cottonq~impfab)
summary(Mod04)$adj.r.squared
abline(Mod04, col=2)

plot(cottonq~expfab)
Mod05 = lm(cottonq~expfab)
summary(Mod05)$adj.r.squared
abline(Mod05, col=2)



Mod06 = lm(cottonq~whoprice+quarter)
summary(Mod06)$adj.r.squared

Mod07 = lm(cottonq~whoprice+year)
summary(Mod07)$adj.r.squared

Mod08 = lm(cottonq~whoprice+impfab)
summary(Mod08)$adj.r.squared #Mejor modelo

Mod09 = lm(cottonq~whoprice+expfab)
summary(Mod09)$adj.r.squared