[R] Colorramp in Maptools, how to choose min and max values for the fg= argument

schaber kschaber at ipp.mpg.de
Tue Sep 21 17:42:25 CEST 2010


Hello,

I am using maptools for plooting geographical data.
The colour of the region indicates some region dependent value 
(population for example).

I pass the colours of the regions to the plot.Map function by defining 
the foreground colour:

jet.colors = colorRampPalette(c("#00007F", "blue", "#007FFF",  "cyan", 
"#7FFF7F", "yellow", "#FF7F00", "red", "#7F0000"))
n=100
cols <- jet.colors(n)
Intervalls =  cut(as.numeric(Vector),n, na.rm=TRUE)
fgs <-cols[Intervalls] ## is there some option/possibility here to 
choose colours differently ??
plot.Map(Shape.map, fg=fgs, ol=NA, bty="n", xlab="", ylab="", xaxt="n", 
yaxt="n")

My problem is the following: I would like to choose minimal and maximal 
value of the colour palette, different from the minimal and maximal 
values of the Vector. For example: Vector=c(2,3,4,5,6), but the maximal 
colour should correspond to 10 and the minimal to 0.

I know, that maptools is not the most actual solution to plot maps, but 
I am building on an old code and therefore do not want to change it.

I would very much appreciate any help or hints!!
Katrin
 


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