# Kod 4.4. Funkcji pozwalająca na porównanie dwóch państw ze względu na wybraną charakterystykę
compare2 <-function(Country1="Germany", Country2="Poland", no_var=4, N_perm=1000) {
oecd1=oecd[oecd$Country==Country1,]
oecd2=oecd[oecd$Country==Country2,]
oecd12=rbind(oecd1,oecd2)
oecd12$Country=as.factor(oecd12$Country)
s1=oecd12[,no_var][oecd12$Country==Country1]
n1=length(s1)
s2=oecd12[,no_var][oecd12$Country==Country2]
n2=length(s2)
T0=abs(mean(s1)-mean(s2))
s=c(s1,s2); n=n1+n2
T=c()
for (n_sim in 1:N_perm) {
s_sam=sample(s)
T=c(T,abs(mean(s_sam[1:n1])-mean(s_sam[(1+n1):n])))
}
par(mfrow=c(2,1))
plot(oecd12[,no_var]~oecd12$Country,main=names(oecd[ no_var]),xlab='Country',ylab=names(oecd[no_var]),col=2:3)
hist(T,main=" ",col=4)
points(T0,0,bg='black',pch=21)
p_val=sum(T>=T0)/N_perm
list( "T"=T, "var"=names(dane[no_var]),"N-perm"=N_perm,"sT" = summary(T),"T0"=T0,"p.value"=p_val)
}