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

hadley wickham h.wickham at gmail.com
Fri Jan 5 01:01:33 CET 2007

Hi Claudia,

It's quite easy to do this using ggplot, although you get exactly the
same appearance as filled.contour (hopefully in the next version).
Have a look at ggtile and scgradient.



On 1/4/07, Claudia Tebaldi <tebaldi at rap.ucar.edu> wrote:
> 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
> http://www.image.ucar.edu/~tebaldi
> currently visiting
> Center for Environmental Science and Policy
> Stanford University
> tel:   (650) 724-9261
> skype: claudia.tebaldi
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