R/Plot_Compare_Binomial_Poisson.R

In likanzhan/acqr: Functions Helping You understand Statistics Easily

#' Draw a graph to compare the binomial and Possion distribution
#' @export

Plot_Compare_Binomial_Poisson <- function(
                                          pi = 0.1,
                                          size = 100) {
  xx <- 0:size
  db <- rep(xx, round(dbinom(xx, size, pi) * 100000, 0))
  db <- ecdf(db)
  dbb <- db(xx)
  lambda <- size * pi
  dp <- rep(xx, round(dpois(xx, lambda) * 100000, 0))
  dp <- ecdf(dp)
  dpp <- dp(xx)
  plot(db,
    col = "blue", cex.points = 1 / log10(size),
    xlab = "X", ylab = "Cumulative Distribution Function",
    main = bquote(pi == .(pi) ~ ", size" == .(size))
  )
  plot(dp, add = TRUE, col = "red", cex.points = 1 / log10(size))
  legend("bottomright",
    col = c("blue", "red"), lty = 1, bty = "n",
    legend = c("Binomial Distribution", "Poisson Distribution")
  )
}