Thanks to everyone who weighed in on this. I found a naive solution that was good enough for my needs, and it may take me a bit to get the subtleties of your comments.
On Nov 26, 2013, at 2:12 AM, Barry Rowlingson <b.rowling...@lancaster.ac.uk> wrote: > On Tue, Nov 26, 2013 at 9:58 AM, Prof Brian Ripley > <rip...@stats.ox.ac.uk> wrote: > >>> But the image function (and probably levelplot) doesn't allow that so >> >> Mis-information alert! The help says >> >> col: a list of colors such as that generated by ‘rainbow’, >> ‘heat.colors’, ‘topo.colors’, ‘terrain.colors’ or similar >> functions. >> >> and look at what they generate. Or see e.g. ?col2rgb . >> >> Although base graphics has the concept of a palette of colours, AFAIK it >> has always been bolted on top of a general colour specification, >> originally RGB and for many years already RGBA. > > > Yes image allows you to specify col=, but it always specifies a > palette. The matrix values are scaled from 1:length(col) and looked up > in that palette. You can't call image with z as matrix of colours and > get those colours, nor set col to a matrix of colours and a see those > colours laid out. This is unlike points() where specifying col= as a > vector of the same length as the number of points gives you a 1:1 > mapping of points to colours. > > To do image() with a 1:1 mapping of cell values to colours requires a > tiny bit of hoop-jumping. > > Barry > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. Don McKenzie Research Ecologist Pacific Wildland Fire Science Lab US Forest Service Affiliate Professor School of Environmental and Forest Sciences University of Washington d...@uw.edu ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
