Monthly Archives: February 2013

The Paul Tol 21-color salute

You may or may not know that PerformanceAnalytics contains a number of specific color schemes designed for charting data in R (they aren’t documented well, but they show up in some of the chart examples). I’ve been collecting color palates for years in search of good combinations of attractiveness, relative weight, and distinctiveness, helped along the way by great sites like ColorBrewer and packages like RColorBrewer.   I’ve assembled palettes that work for specific purposes, such as the color-focus palates (e.g., redfocus is red plus a series of dark to light gray colors). Others, such as rich#equal, provide a palette for displaying data that all deserve equal treatment in the chart. Each of these palettes have been designed to create readable, comparable line and bar graphs with specific objectives outlined before each category below.

I use this approach rather than generating schemes on the fly for two reasons: it creates fewer dependencies on libraries that don’t need to be called dynamically; and to guarantee the color used for the n-th column of data.

Oh, and here’s a little utility function (that I don’t think I wroteEDIT: that I know I didn’t write, since it was written by Achim Zeileis and is found in his colorspace package, but I have carried it around for quite a while) for displaying a palette:

# Function for plotting colors side-by-side
pal <- function(col, border = "light gray", ...){
  n <- length(col)
  plot(0, 0, type="n", xlim = c(0, 1), ylim = c(0, 1),
       axes = FALSE, xlab = "", ylab = "", ...)
  rect(0:(n-1)/n, 0, 1:n/n, 1, col = col, border = border)
}

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