[R] color of opposite sign values in filled.contour

[Claudia Tebaldi]

Dear R-helpers,

I'm plotting geophysical data in the form of contours using
"filled.contour". The display would be much more effective if the areas
with negative values could be color coded
by -- say -- "cold colors" in the range of blue to green, and conversely
the areas with positive values got plotted with "warm colors", from yellow
to red.
Right now if I use a palette spanning the spectrum I need the entire range
is associated with the actual range of the data, which can be positively
or negatively skewed, and as a result the position of the zero is totally
arbitrary.
I'm wondering if someone out there has come up with a clever way to set
the color scale accordingly, as a function of the actual range of the
values in the matrix that is being plotted. Ideally, it would be neat to
still use the entire spectrum, but sampling differently the cold and warm
subsets accordingly to the extent of the negative and positive values in
the data.

Also, when I try to play around in an ad hoc fashion with the palette I
often get funny results in the legend, with color-scale wrapping or blank
cells at one of the extremes. I cannot hack effectively the code of the
filled.contour function, obviously...


Thank you in advance for your help
& happy new year

claudia tebaldi











-- 
Claudia Tebaldi
ISSE/CGD/IMAGe
http://www.image.ucar.edu/~tebaldi

currently visiting
Center for Environmental Science and Policy
Stanford University
tel:   (650) 724-9261
skype: claudia.tebaldi