plot with confidence intervals

## modified version of the code I found on the web.
## I forgot who wrote the origial version

plotCI <- function (x, y = NULL, uiw, liw = uiw, ylim=NULL,..., sfrac = 0.01)  {
 col2 = 'gray'
 if (is.list(x)) {
   y <- x$y
   x <- x$x
 }
 if (is.null(y)) {
   if (is.null(x))
     stop("both x and y NULL")
   y <- as.numeric(x)
   x <- seq(along = x)
 }
 ui <- y + uiw
 li <- y - liw
 if(is.null(ylim)) {
   plot(x, y, ylim = range(c(y, ui, li),na.rm=T), ...)} else
   {plot(x, y, ylim = ylim, ...)}
 smidge <- diff(par("usr")[1:2]) * sfrac
 segments(x, li, x, ui,col=col2)
 x2 <- c(x, x)
 ul <- c(li, ui)
 segments(x2 - smidge, ul, x2 + smidge, ul,col=col2)
 if(is.null(ylim))  ylim=range(c(y, ui, li),na.rm=T)
 points(x, y, ...)
 invisible(list(x = x, y = y))
}