# -----------------------------------------------------------------------
urna <- c(rep("Bianca",7),rep("Nera",3))
nrep <- 1000
out <- rep(NA,nrep)

for (i in 1:nrep)
{
    x <- sample(urna,4,replace=FALSE)
    y <- sum(x == "Bianca")
    out[i] <- y
}

table(out)
# -----------------------------------------------------------------------



# -----------------------------------------------------------------------
moneta <- c("TESTA","CROCE")
nrep <- 100000

st.1 <- system.time(x <- sample(moneta,nrep,replace=TRUE))

st.2 <- system.time(
{
   x <- rep(NA,nrep)
   for (i in 1:nrep) x[i] <- sample(moneta,1)
}
)

st.2[3] - st.1[3]
st.2[3] / st.1[3]
# -----------------------------------------------------------------------