Warp colors in a color ramp

Usage

warpRamp(
  ramp,
  lens = 5,
  divergent = TRUE,
  expandFactor = 10,
  plot = FALSE,
  verbose = FALSE,
  ...
)

Arguments

ramp: character vector of R colors
lens: numeric lens factor, centered at zero, where positive values cause colors to change more rapidly near zero, and negative values cause colors to change less rapidly near zero and more rapidly near the extreme.
divergent: logical indicating whether the ramp represents divergent colors, which are assumed to be symmetric above and below zero. Otherwise, colors are assumed to begin at zero.
expandFactor: numeric factor used to expand the color ramp prior to selecting the nearest warped numeric value as the result of warpAroundZero(). This value should not need to be changed unless the lens is extremely high (>100).
plot: logical indicating whether to plot the input and output color ramps using showColors().
verbose: logical indicating whether to print verbose output.
...: additional parameters are passed to showColors().

Value

character vector of R colors, with the same length as the input vector ramp.

Details

This function takes a vector of colors in a color ramp (color gradient) and warps the gradient using a lens factor. The effect causes the color gradient to change faster or slower, dependent upon the lens factor.

The main intent is for heatmap color ramps, where the color gradient changes are not consistent with meaningful numeric differences being shown in the heatmap. In short, this function enhances colors.

Examples

BuRd <- rev(RColorBrewer::brewer.pal(11, "RdBu"));
BuRdPlus5 <- warpRamp(BuRd, lens=2, plot=TRUE);

BuRdMinus5 <- warpRamp(BuRd, lens=-2, plot=TRUE);


Reds <- RColorBrewer::brewer.pal(9, "Reds");
RedsL <- lapply(nameVector(c(-10,-5,-2,0,2,5,10)), function(lens){
   warpRamp(Reds, lens=lens, divergent=FALSE)
});
showColors(RedsL);