Draw Confidence Band

Draw a band using a simple syntax. Just a wrapper for the function polygon() typically used to draw confidence bands.

DrawBand(x, y, col = SetAlpha("grey", 0.5), border = NA)

Arguments

x

a vector or a matrix with x coordinates for the band. If x is given as matrix it must be a \(2 \times n\) matrix and the second column will be reversed. x will be recyled in the case y is a 2dimensional matrix.

y

a vector or a matrix with y coordinates for the band. If y is given as matrix it must be a \(2 \times n\) matrix and the second column will be reversed. y will be recyled in the case x is a 2dimensional matrix.

col

the color of the band.

border

the border color of the band.

Author

Andri Signorell <andri@signorell.net>

See also

polygon

Examples

set.seed(18)
x <- rnorm(15)
y <- x + rnorm(15)

new <- seq(-3, 3, 0.5)
pred.w.plim <- predict(lm(y ~ x), newdata=data.frame(x=new), interval="prediction")
pred.w.clim <- predict(lm(y ~ x), newdata=data.frame(x=new), interval="confidence")

plot(y ~ x)
DrawBand(y = c(pred.w.plim[,2], rev(pred.w.plim[,3])),
  x=c(new, rev(new)), col= SetAlpha("grey90", 0.5))

# passing y as matrix interface allows more intuitive arguments
DrawBand(y = pred.w.clim[, 2:3],
         x = new, col= SetAlpha("grey80", 0.5))

abline(lm(y~x), col="brown")