On 02/04/2010 05:56 AM, Everton Emanuel wrote:
Dear all,
I want to display a "compass rose" on a map, but I have no idea how
to do that. Do you know how can I display a compass rose on a map?
Hi Everton,
Here's a very basic compass rose function. rot is in degrees. I'll tart
it up a bit and put it in the next version of plotrix, unless the Geo
people think it should go in one of the mapping packages.
Jim
compassRose<-function(x,y,rot=0,cex=1) {
oldcex<-par(cex=cex)
mheight<-strheight("M")
xylim<-par("usr")
plotdim<-par("pin")
xmult<-(xylim[2]-xylim[1])/(xylim[4]-xylim[3])*plotdim[2]/plotdim[1]
point.angles<-seq(0,7*pi/4,by=pi/4)+pi*rot/180
crspans<-rep(c(mheight*3,mheight/2),4)
xpoints<-cos(point.angles)*crspans*xmult+x
ypoints<-sin(point.angles)*crspans+y
polygon(xpoints,ypoints)
txtxpoints<-cos(point.angles[c(1,3,5,7)])*1.33*crspans[1]*xmult+x
txtypoints<-sin(point.angles[c(1,3,5,7)])*1.33*crspans[1]+y
text(txtxpoints,txtypoints,c("E","N","W","S"))
par(oldcex)
}
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