[R] legend

[Paul Murrell]

Hi


Uwe Ligges wrote:
> Thomas Steiner wrote:
> 
> 
>>I color some area grey with polygon() (with a red border) and then I
>>want to have the dashed red border in the legend as well. How do I
>>manage it?
>>
>>And I want to mix (latex) expressions with text in my legend.
> 
> 
> 
> Both points are not that easy to solve, hence I'd like to suggest to 
> write your own little function that generates the legend.
> 
> Starting at the upper left, calculating the stringheight, painting the 
> (party very special) symbols, and adding the text line by line seems to 
> be the most easiest solution here (which is not that nice, though.


I don't think it's too bad.  For example, try replacing the original ...

legend(x=0,y=3.5,legend=c("exp(0.7x)","mu=0.7, sigma=0.4","mu=0.7,
sigma=0.2","mu=0.7, sigma=0.1","Standardabweichung fÃ¼r 
sigma=0.2"),lwd=c(4,4,4,4,12),col=c(cs,"grey"),bg="transparent",cex=1.15)

... with ...

# Use grid and gridBase so you've got some sensible
# coordinate systems to work within
library(grid)
library(gridBase)
# Align a grid viewport with the plotting region
vps <- baseViewports()
pushViewport(vps$inner, vps$figure, vps$plot)
# Define labels and colours
# Labels are mathematical expressions
labels <- expression("exp(0.7x)",
     list(mu == 0.7,sigma == 0.4),
     list(mu == 0.7,sigma == 0.2),
     list(mu == 0.7, sigma == 0.1),
     paste("Standardabweichung fÃ¼r ",sigma == 0.2))
cols <- cs
# Draw each legend item on its own line
# Top line 1cm in from top-left corner
for (i in 1:5) {
   x <- unit(1, "cm")
   y <- unit(1, "npc") - unit(1, "cm") - unit(i, "lines")
   if (i < 5) {
     grid.lines(unit.c(x, unit(2, "cm")), y + unit(0.5, "lines"),
                gp=gpar(col=cols[i], lwd=3))
   } else {
     grid.rect(x, y, width=unit(1, "cm"),
               height=unit(1, "lines"),
               gp=gpar(fill="grey", col=cs[3], lty="dashed"),
               just=c("left", "bottom"))
   }
   grid.text(labels[i], x + unit(1.5, "cm"), y,
             just=c("left", "bottom"))
}
# clean up
popViewport(3)

... that's a bit of typing, but if you need to do more than one, it 
would go inside a function with labels and cols as arguments (and '5' 
replaced by 'length(labels)') without too much trouble.

(In this case, you could also pretty easily just do the main plot using 
grid and avoid having to use gridBase.)

Paul


>>Just execute my lines below and you know want I mean. Or pass by at
>>http://de.wikipedia.org/wiki/Bild:GBM.png to see the picture online.
>>
>>Thomas
>>
>>
>>bm <- function(n=500, from=0, to=1) {
>>  x=seq(from=from,to=to,length=n)
>>  BM<-c(0,cumsum(rnorm(n-1,mean=0,sd=sqrt(to/n))))
>>  cbind(x,BM)
>>}
>>gbm <- function(bm,S0=1,sigma=0.1,mu=1) {
>>  gbm=S0
>>  for (t in 2:length(bm[,1])) {
>>    gbm[t]=S0*exp((mu-sigma^2/2)*bm[t,1]+sigma*bm[t,2])
>>  }
>>  cbind(bm[,1],gbm)
>>}
>>
>>set.seed(9826064)
>>cs=c("dark green", "steelblue", "red", "yellow")
>>
>>#png(filename = "GBM.png", width=1600, height=1200, pointsize = 12)
>>par(bg="lightgrey")
>>x=seq(from=0,to=1,length=500)
>>plot(x=x, y=exp(0.7*x), type="n", xlab="Zeit", ylab="", ylim=c(1,3.5))
>>polygon(x=c(x,rev(x)),
>>y=c(exp(0.7*x)+0.4*sqrt(x),rev(exp(0.7*x)-0.4*sqrt(x))), col="grey",
>>border=cs[3], lty="dashed")
>>lines(x=x,y=exp(0.7*x), type="l", lwd=3, col=cs[1])
>>lines(gbm(bm(),S0=1,mu=0.7,sigma=0.4), lwd=3, col=cs[2])
>>lines(gbm(bm(),S0=1,mu=0.7,sigma=0.2), lwd=3, col=cs[3])
>>lines(gbm(bm(),S0=1,mu=0.7,sigma=0.1), lwd=3, col=cs[4])
>>title(main="Geometrische Brownsche Bewegung",cex.main=2.5)
>>legend(x=0,y=3.5,legend=c("exp(0.7x)","mu=0.7, sigma=0.4","mu=0.7,
>>sigma=0.2","mu=0.7, sigma=0.1","Standardabweichung für 
>>sigma=0.2"),lwd=c(4,4,4,4,12),col=c(cs,"grey"),bg="transparent",cex=1.15)
>>#dev.off()
>>
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> 
> 
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-- 
Dr Paul Murrell
Department of Statistics
The University of Auckland
Private Bag 92019
Auckland
New Zealand
64 9 3737599 x85392
paul at stat.auckland.ac.nz
http://www.stat.auckland.ac.nz/~paul/