[R] Plotting a grid of directly specified colours

[Barry Rowlingson]

On Thu, Nov 4, 2010 at 4:00 PM, Peter Davenport <pwdavenport at gmail.com> wrote:
> Dear R-help,
>
> Could any of you direct me to a function for plotting a grid of colours,
> directly specified by a matrix of hex colour codes?  In other words I'm
> looking for a heatmap() or image()-like function to which I can specify the
> colour of each grid location directly, rather than providing a numerical
> matrix and a 1D-colour scale (heatmap, image, levelplots,NeatMap...). I'm
> surprised I haven't found anything simple with RSiteSearch,
> help.search, net.
>
> I'd like to use this function to encode one variable as "chroma" and a
> second as "luminance" (hcl colour space), so that the two variables can be
> visualised in a single heatmap (the variable are fold-change and a q-value,
> a significance measure). If anyone has any thoughts/warnings to offer re
> this idea then I'd love to hear them (it must have been tried before, but
> I've not come across any examples) .

 I've kludged this kind of thing in the past. Create a matrix of
1:(nrow*ncol), and specify the col as your colour matrix.

Example:

m = matrix(c("red","green","blue","yellow","orange","black"),2,3)
mc = matrix(1:(nrow(m)*ncol(m)),nrow(m),ncol(m))
image(mc,col=m)

Barry