# Created by James Holland Jones (http://monkeysuncle.stanford.edu/?p=485)

error.bar = function(x, y, upper, lower=upper, length=0.1,...){
 if(length(x) != length(y) | length(y) !=length(lower) | length(lower) != length(upper))
  stop("vectors must be same length")
  arrows(x,y+upper, x, y-lower, angle=90, code=3, length=length, ...)
}