Rescale Values to lie in a Given Range

This is helpful in e.g. developing a color scale for an image plot. It is not necessary that rlow be less than rhigh, and in fact reversing them is a good way to get a reversed color scale for a plot.

rescale(x, xlow, xhigh, rlow = 0, rhigh = 1, clip = TRUE)

Arguments

x: a numeric vector.
xlow: x value to correspond to rlow. If not given, it will be calculated as the minimum value of x
xhigh: x value to correspond to rhigh. If not given, it will be calculated as the maximum value of x
rlow: value of the result corresponding to x equal to xlow.
rhigh: value of the result corresponding to x equal to xhigh.
clip: logical, set to TRUE to clip the result to the range spanned by rlow and rhigh.

Value

A new vector, which has minimum lim[1] and maximum lim[2].

Author

Dan Kelley

Examples

library(oce)
# Fake tow-yow data
t <- seq(0, 600, 5)
x <- 0.5 * t
z <- 50 * (-1 + sin(2 * pi * t / 360))
T <- 5 + 10 * exp(z / 100)
palette <- oce.colorsViridis(100)
zlim <- range(T)
drawPalette(zlim = zlim, col = palette)
plot(x, z,
    type = "p", pch = 20, cex = 3,
    col = palette[rescale(T, xlow = zlim[1], xhigh = zlim[2], rlow = 1, rhigh = 100)]
)