Thanks Roger,
your trick worked, reworking the polygon data to a raster and plotting
the file with image()
and then plotting the rest with plot(...., add=TRUE) works great (see
attached code).
It shows that the famous KISS principle (keep is simple, stupid ) also
applies to plotting maps
in R .......
Peter
## code
image(rasterdata["n"], col=colors)
plot(radarcirkels, add=TRUE)
plot(circle2, add= TRUE)
plot(turbines, pch=18, add= TRUE, col = 'red')
plot(metmast, pch = 19, col = 'blue', add= TRUE)
plot(raster,pch=my.symbols(raster.midpoint$raster.mid.x1,raster.midpoint$raster.mid.x2,
ms.arrows, angle= Data$rad, inches=0.5, adj=0.5, lwd=1.5, code =
2, col = 'blue'), lty="blank",
add=TRUE)
##code
Roger Bivand schreef:
On Wed, 4 Feb 2009, Peter van Horssen wrote:
Dear all,
I have a plot problem which is related to the 'contourlines on a plot
question' from a while ago.
I have a map with 144 polygons (squares), for each square we
calculate the mean flight direction (of birds).
What I try to plot is a map with the samplesize as a
greyscale in the polgons and an arrow on top depicting the mean
direction of that square.
The polygonmap with greyscale is easily plotted with spplot.
The arrows with mean direction are a bit more difficult. Most sources
point towards the 'grid' package or towards arrows(). Both draw arrows
with xy pairs (form > to) in graph coordinates.
However 'mysymbols' in the library TeachingDemos plots a arrow symbol
with a direction 'dir' (in radians) and a fixed length, just what I
need.
Unfortunately these arrows only plot with 'plot' command (see
attached code) and therefore do not allign
with the plot resulting from ssplot. As you can see the arrows are
plotted as a pch 'symbol'.
If you try to use only base graphics, you may find this easier to sort
out initially - so make the greyscale plot with image() if the data
are gridded or plot() if irregular polygons - more intervention will
be needed to choose the colours and to provide a legend, then overplot
using my.symbols(), which seems to be a base graphics function, if
I've found the right one. Otherwise you'll need to find a way to draw
the arrows by for example constructing a SpatialLines object of
arrows, and using sp.lines in the sp.layout= argument.
Hope this helps,
Roger
I tried to construct a 'sp.points' element for the sp.layout
with the my.symbols ( .....) argument but this doesn't work
The arrow.sp$pch is NULL and when I manually force the my.symbol(..)
in it by :
####
arrow.sp$pch <-
my.symbols(raster.midpoint$raster.mid.x1,raster.midpoint$raster.mid.x2,ms.arrows,
angle= Data$rad, inches=0.5, adj=0.5, lwd=1.5, code = 2, col = 'blue')
####
the spplot command generates an error
Question:
is there an obvious solution tot this (relative simple) problem ?
if not, is there a way to 'allign' de plots from spplot and plot (the
arrowplot) ?
thanks in advance
##plot raster##
radarcirkels.sp <- list("sp.polygons", radarcirkels)
circle2.sp <- list("sp.polygons", circle2, add= TRUE)
turbines.sp <- list("sp.points", turbines, pch=18, add= TRUE, col =
red')
metmast.sp <- list("sp.points", metmast, pch = 19, col = 'red', add=
TRUE)
turbine.radar.layout <- list(radarcirkels.sp, circle2.sp,
turbines.sp, metmast.sp)
colors <- shadepalette("darkgreen","white",n=20)
spplot (raster1["n"],col.regions=colors,at=c(0,10,50,100,200,300),
sp.layout = turbine.radar.layout)
##plot arrows ##
library(TeachingDemos)
plot(raster)
plot(radarcirkels, add=TRUE)
plot(circle2, add= TRUE)
plot(turbines, pch=18, add= TRUE, col = 'red')
plot(metmast, pch = 19, col = 'blue', add= TRUE)
plot(raster,pch=my.symbols(raster.midpoint$raster.mid.x1,raster.midpoint$raster.mid.x2,
ms.arrows, angle= Data$rad, inches=0.5, adj=0.5, lwd=1.5, code =
2, col = 'blue'), add=TRUE)
--
================================
Peter van Horssen
Bureau Waardenburg bv
Adviseurs voor ecologie & milieu
Postbus 365
4100 AJ Culemborg
Tel: 0345-512710
Fax: 0345-519849
e-mail: p.w.van.hors...@buwa.nl
================================
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