dichromat (version 1.1)

colorRampPalette: Extend a color palette to a color ramp

Description

These functions are useful for converting hand-designed `sequential' or `diverging' color schemes into continous color ramps eg for image and filled contour plots. Unfortunately the interpolation is still in RGB space.

Usage

colorRampPalette(palette, bias = 1,method=c("spline","linear"))
colorRamp(palette, bias=1,method=c("spline","linear"))

Arguments

palette

A vector of colors

bias

Bias >1 puts more colors at high values,

method

Interpolation method. Spline interpolation gives better results but can end up outside the valid RGB space with highly saturated palettes or those based on a small starting set.

Value

• colorRampPalette returns a palette generating function like terrain.colors or heat.colors that takes an integer argument and generates a palette with that many colors.

  colorRamp returns a color generating function, that takes a number between 0 and 1 and generates the corresponding color.

See Also

www.colorbrewer.org

Examples

m<-outer(1:20,1:20,function(x,y) sin(sqrt(x*y)/3))

   redblue<-colorRampPalette(c("red","orange","blue"),method="linear")
   filled.contour(m,color.palette=redblue)

   yb<-colorRampPalette(c("yellow2","goldenrod","darkred"))
   filled.contour(m,color.palette=yb)

   yb<-colorRampPalette(c("yellow2","goldenrod","darkred"),bias=0.5)
   filled.contour(m,color.palette=yb)

   ## Two ColorBrewer sequential palettes
   ylOrBn4<-c("#FFFFD4", "#FED98E", "#FE9929","#CC4C02")
   ylGnBl5<-c("#FFFFCC","#C7E9B4","#7FCDBB","#40B6C4","#2C7FB8" ,"#253494")

   ylOrBn<-colorRampPalette(ylOrBn4,method="linear")
   ylGnBl<-colorRampPalette(ylGnBl5)
   filled.contour(m,color.palette=ylOrBn)
   filled.contour(m,color.palette=ylGnBl)