R/auc.r

In kulife: Datasets and functions from the (now non-existing) Faculty of Life Sciences, University of Copenhagen

auc <- function(x, y, from=min(x), to=max(x), ...) {

  if (length(x) != length(y))
    stop("x and y must have the same length")

  if (length(unique(x))<2)
    return(NA)

  values <- approx(x, y, xout=sort(unique(c(from, to, x[x>from & x<to]))),...)

  res <- .5*sum(diff(values$x)*(values$y[-1]+values$y[-length(values$y)]))
  res
}