grDevices

The colorRamp() and colorRampPalette() functions in {grDevice} package allow generating gradient colors that can be used in creating color scales.

Working examples:

library(grDevices)

colorRamp(c("red", "blue"))((0:4)/4)

##        [,1] [,2]   [,3]
## [1,] 255.00    0   0.00
## [2,] 191.25    0  63.75
## [3,] 127.50    0 127.50
## [4,]  63.75    0 191.25
## [5,]   0.00    0 255.00

The output from colorRamp() is a function that can return a numerical matrix. The matrix essentially represents colors in RGB values (red, green, and blue respectively), with both the initially-defined and interpolated colors. Let’s now take a look at colorRampPalette():

colorRampPalette(c("red", "blue"))(5)

## [1] "#FF0000" "#BF003F" "#7F007F" "#3F00BF" "#0000FF"

The output from colorRampPalette(), different from colorRamp(), is a function that returns a fixed number (five in this case) of colors in HEX codes.

RColorBrewer

The brewer.pal() function in {RColorBrewer} package would call out one of the pre-defined color palettes that one wish to use.

library(RColorBrewer)
par(mar=c(3,4,2,2))
display.brewer.all()

Say you’d like to get three colors from Set1:

brewer.pal(3, "Set1")

## [1] "#E41A1C" "#377EB8" "#4DAF4A"

Take home message: {RColorBrewer} only offer a limited number of options to choose from, which is a good starting point, whereas {grDevices} is much more flexible.

More on color scales: {grDevices} and {RColorBrewer}

grDevices

RColorBrewer