The matrix2png web or command-line tool is a very simple option and doesn't require as much data munging as R options, IME.

Try:

enc = c(53.89,54.87,42.61,48.34,46.93,49.53,47.04,51.97,51.23,52.06) 
GC3 = c(40.7, 55.8, 35, 31.1, 75.2, 36.4, 36.3,66.9, 31.2, 41.3)
image(cbind(enc, GC3)

Then customise the scales.

Try heatmap.2 in the R gplots package.

Yeah, that would be the "simplest" solution for basic heatmaps I'd say. I've put up a tutorials a few years ago, hopefully it helps regarding the details: A short tutorial for decent heat maps in R

Try heatmap.2 in the R gplots package.

dears this link is good: http://www.compbiome.com/2010/04/r-heatmaps-with-gplots.html

Genesis (http://genome.tugraz.at/genesisclient/genesisclient_description.shtml) is a free software.