foot <- read.table("DATA/lrm-foot.txt",header=T)
summary(foot)

is.factor(foot$sex)

plot(foot$foot.L, foot$body.H, xlab='Delka chodidla (mm)', ylab='Telesna vyska (mm)', type='n')
points(foot$foot.L[foot$sex=='f'], foot$body.H[foot$sex=='f'], pch=1, col='red')
points(foot$foot.L[foot$sex=='m'], foot$body.H[foot$sex=='m'], pch=2, col='blue')
legend("topleft", c("zena", "muz"), pch = c(1,2), col=c('red', 'blue'))

table(foot$sex)
##
## f m
## 70 47
nrow(foot)
## [1] 117
mean(foot$body.H[foot$sex=='f'])
## [1] 1670.771
sd(foot$body.H[foot$sex=='f'])
## [1] 71.26927
mean(foot$body.H[foot$sex=='m'])
## [1] 1780.064
sd(foot$body.H[foot$sex=='m'])
## [1] 58.38456
mean(foot$body.H)
## [1] 1714.675
sd(foot$body.H)
## [1] 85.25619
mean(foot$foot.L[foot$sex=='f'])
## [1] 244.3714
sd(foot$foot.L[foot$sex=='f'])
## [1] 11.43497
mean(foot$foot.L[foot$sex=='m'])
## [1] 266.2128
sd(foot$foot.L[foot$sex=='m'])
## [1] 11.46248
mean(foot$foot.L)
## [1] 253.1453
sd(foot$foot.L)
## [1] 15.66914

model.interakce <- lm(body.H ~ sex * foot.L, data=foot)
model.bez.int <- lm(body.H ~ sex + foot.L, data=foot)
anova(model.bez.int, model.interakce)

par(mfrow=c(2,2))
plot(model.bez.int)

shapiro.test(model.bez.int$residuals)

t.test(model.bez.int$residuals)

library(car)

durbinWatsonTest(model.bez.int)

summary(model.bez.int)

model.bez.int.bez.faktoru <- lm(body.H ~ foot.L, data=foot)
anova(model.bez.int.bez.faktoru, model.bez.int)

par(mfrow=c(2,2))
plot(model.bez.int.bez.faktoru)

summary(model.bez.int.bez.faktoru)

xx <- seq(min(foot$foot.L), max(foot$foot.L), length=300)
interval.spol <- predict(model.bez.int.bez.faktoru,newdata=data.frame(foot.L=xx),
                         interval='confidence')
plot(foot$foot.L, foot$body.H, xlab='Delka chodidla (mm)', ylab='Telesna vyska (mm)', type='n')
points(foot$foot.L[foot$sex=='f'], foot$body.H[foot$sex=='f'], pch=1, col='red')
points(foot$foot.L[foot$sex=='m'], foot$body.H[foot$sex=='m'], pch=2, col='blue')
lines(xx,interval.spol[,1])
lines(xx,interval.spol[,2], lty=2)
lines(xx,interval.spol[,3], lty=2)
legend("topleft", c("zena", "muz"), pch = c(1,2), col=c('red', 'blue'))