#Priklad 1.1:
data <- read.delim('znamky.txt', header=F)
head(data)
f1 <- factor(data$V1, levels=c(1,2,3,4),
             labels=c('vyborne', 'chvalitebne', 'dobre', 'nedostatecne'))

f2 <- factor(data$V2, levels=c(1,2,3,4),
             labels=c('vyborne', 'chvalitebne', 'dobre', 'nedostatecne'))

f3 <- factor(data$V3, levels=c(0,1),
             labels=c('zena', 'muz'))

data2 <- data.frame(f1, f2, f3)
head(data2)

names(data2) <- c('matematika', 'anglictina', 'pohlavi')
head(data2)


#=================================================================================
#Priklad 1.2
#Variacni rada
matematika <- data2$matematika
(n1 <- sum(matematika=='vyborne'))
(n2 <- sum(matematika=='chvalitebne'))
(n3 <- sum(matematika=='dobre'))
(n4 <- sum(matematika=='nedostatecne'))

nj <- c(n1, n2, n3, n4)

(n <- sum(nj))
(pj <- nj/n)
(Nj <- cumsum(nj))
(Fj <- cumsum(pj))

(variacni.rada <- data.frame(nj, Nj, pj, Fj))
row.names(variacni.rada) <- c('vyborne', 'chvalitebne', 'dobre', 'nedostatecne')
variacni.rada

#------------------------------------------------------------------------------------------------------
# Barplot
nazvy.znamek <- c('vyborne', 'chvalitebne', 'dobre', 'nedostatecne')
barplot(nj,
        xlab='Znamka',
        ylab='Pocet pozorovani',
        main='Sloupkovy graf',
        names=nazvy.znamek,
        col='blue',
        border='darkblue',
        density=20
        )

abline(h=0:9, col='grey80', lty=2)

#------------------------------------------------------------------------------------------------------
#Polygon cetnosti
plot(1:4, nj,
     xlab='Znamka',
     ylab='Absolutni cetnost',
     main='Polygon cetnosti',
     xlim=c(0.5,4.5),
     ylim=c(1,9),
     type='n',
     axes=F
     )

abline(h=0:9, col='grey80', lty=2)
abline(v=0:9, col='grey80', lty=2)

lines(1:4, nj, col='darkblue', lwd=2)
points(1:4, nj, col='darkblue', pch=20, cex=2)

axis(1, at=1:4, lab=nazvy.znamek)
axis(2, at=0:10)

box()

#=================================================================================
#Priklad 1.6
data <- read.delim('lebky.txt', header=F)
head(data)
names(data) <- c('delka', 'sirka', 'pohlavi')

data.M <- data[data$pohlavi=='muž', ]
data.M
range(data.M$delka)
(n.M <- dim(data.M)[1])

(Sturgers <- round(1+3.3*log(n.M,10),0))
199-164

#=================================================================================
#Priklad 1.7
delka.M <- data.M$delka
hist(delka.M,
     breaks=seq(163, 199, by=4),
     xlab='Delka lebky',
     ylab='Pocetnosti',
     main='Histogram',
     ylim=c(0, 52),
     col='blue',
     border='darkblue',
     density=20,
     axes=F
     )

abline(h=seq(0,60,by=10), col='grey80', lty=2)
axis(1, at=seq(163, 199, by=4))
axis(2, at=seq(0,50, by=10))

abs.c <- hist(delka.M, breaks=seq(163, 199, by=4), plot=F)$counts
stred <- hist(delka.M, breaks=seq(163, 199, by=4), plot=F)$mids
rel.c <- round(abs.c/sum(abs.c)*100, digits=1)

cetnosti <- paste(abs.c, ';', rel.c, '%', sep='')
cetnosti
text(stred, abs.c+2, cetnosti, cex=0.7)