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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