colorRampPalette {geneplotter} | R Documentation

## 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.

### Usage

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

### Arguments

`palette` | A vector of colors
`bias` | Bias >1 puts more colors at high values, <1 puts more at low values
`method` | Interpolation method. Spline interpolation may give smoother results but can end up outside the valid RGB space, especially 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.

### Author(s)

Thomas Lumley

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

       if(require("RColorBrewer")){
            RdBu7<-colorRampPalette(brewer.pal(7,"RdBu"),method="spline")
            RWB<-colorRampPalette(c("red","white","blue"))
            redblue<-colorRampPalette(c("red","blue"))
            filled.contour(m,color.palette=redblue,main="naive red-blue")
            filled.contour(m,color.palette=RWB,main="naive red-white-blue")
            filled.contour(m,color.palette=RdBu7,main="ColorBrewer RdBu7")
       }

[Package geneplotter version 1.5.2 Index]