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

[Jannis]

Hi Katrin,


your problem is not related to maptools, rather to the base function "colorRampPalette". In my opinion the easiest way to get what you want is to use colorRamp:

Vector=c(2,3,4,5,6)
color.ramp <- colorRamp(c('white','black'))
map.colors <- color.ramp(Vector/10)

The 10 refers to the maximum value that you specified. You just have to adjust the colors.


HTH
Jannis


--- schaber <kschaber at ipp.mpg.de> schrieb am Di, 21.9.2010:

> Von: schaber <kschaber at ipp.mpg.de>
> Betreff: [R] Colorramp in Maptools, how to choose min and max values for the fg= argument
> An: r-help at r-project.org
> Datum: Dienstag, 21. September, 2010 15:42 Uhr
> 
> 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
> 
> 
> -----Integrierter Anhang folgt-----
> 
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