[R] fill map with gradient: package?

[Thomas Steiner]

Thanks Paul.
I'm still struggeling with some beginners issues on the ps-import
(windows troubles with installing ghostscript), but when I resolved
them I'm sure that I can use your example code which loos great to me.
Thanks a lot,
Thomas


2009/11/4 Paul Murrell <p.murrell at auckland.ac.nz>:
> Hi
>
>
> Thomas Steiner wrote:
>>
>> Hi,
>> I'd like to fill an existing svg (or png) map with gradient colors.
>> In detail: The file
>>
>> http://commons.wikimedia.org/wiki/File:Karte_%C3%96sterreich_Bundesl%C3%A4nder.svg
>> should be filled with the population density data from this table:
>> http://de.wikipedia.org/wiki/%C3%96sterreich#Verwaltungsgliederung
>> choosing the right color saturation (or whatever). The final result
>> should be something like this map:
>>
>> http://commons.wikimedia.org/wiki/Image:Bevoelkerungsdichte_-_Oesterreich.svg
>> Is there a package or so for these two tasks (filling and color
>> density ploting)?
>
>
> The 'grImport' package can help with getting the SVG into R (see
> http://www.jstatsoft.org/v30/i04).
>
> First step is to convert the SVG to PostScript (I used InkScape - you can
> play around with how the text comes across, but I'm going to ignore that and
> concentrate on the map regions).
>
> Having done that, the following code loads the map into R and draws it ...
>
> library(grImport)
> PostScriptTrace("Austria-Map-withFonts.ps", charpath=FALSE)
> map <- readPicture("Austria-Map-withFonts.ps.xml")
> grid.picture(map)
>
> ... (the orientation may be 90 degrees out and you may get some warnings
> about character encodings;  the former is easy to fix [see below] and the
> latter can just be ignored for now because we are ignoring the text).  The
> next code shows the breakdown of the map into separate "paths" ...
>
> grid.newpage()
> picturePaths(map)
>
> ... from which we can see that the regions are the first 10 paths ...
>
> grid.newpage()
> grid.picture(map[1:10], use.gc=FALSE)
>
> At this point, you can use grImport to draw the regions with different fill
> colours, or you can just extract the x,y coordinates of the regions and
> go-it-alone.  The following code takes the latter path, setting up 10
> different colours, and drawing each region using grid.polygon().  The
> orientation is fixed by pushing a rotated viewport first ...
>
>
> colours <- hcl(240, 60, seq(30, 80, length=10))
> grid.newpage()
> pushViewport(viewport(angle=-90),
>             grImport:::pictureVP(map[1:10]))
> mapply(function(p, col) {
>           grid.polygon(p$x, p$y, default.units="native",
>                        gp=gpar(fill=col))
>       },
>       regions, colours)
>
>
> Hope that helps.
>
> Paul
>
>
>> Thanks for your help,
>> Thomas
>>
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>