quantile quantile plot

qqplot.R

## http://ygc.name/2011/08/02/q-q-plots/

qqplot <- function(y, distribution=qnorm) {
  x <- distribution(ppoints(y))
  plot(x, sort(y),
       xlab="Theoretical Quantiles",
       ylab="Sample Quantiles",
       main="Normal Q-Q Plot"
       )
  lines(y,y)
}

qqplot2 <- function(y, distribution=qnorm) {
  require(ggplot2)
  x <- distribution(ppoints(y))
  d <- data.frame(x=x, y=sort(y))
  p <- ggplot(d, aes(x=x, y=y)) +
    geom_point() +
      geom_line(aes(x=x, y=x)) +
        opts(title="Normal Q-Q Plot") +
          xlab("Theoretical Quantiles") +
            ylab("Sample Quantiles")
  return(p)
}