## function for drawing the binomial distribution with parameters n and p.

binomial.distribution <- function(n, p, ...){
  plot(c(0:n),
       dbinom(c(0:n),n,p),
       type='h',
       xlab = "",
       ylab = "",
       main = paste("n=",n, " p=",p),
       yaxp = c(0, 0.5, 5),
       ...
       )
}

## dividing plot window into 4x3 plots.
par(mfrow = c(4,3))

## drawing binomial distributions for different parameter values.

for (n in c(4,10,20,50)){
  for (p in c(0.2,0.5,0.8)) {
    binomial.distribution(n, p,
                          xlim = c(0,50),
                          ylim = c(0,0.45)
                          )
  }
}

par(mfrow = c(1,1))