Hi,

I would like to add contour lines to a (trellis/lattice-) levelplot.

Sure, there is the "contour=TRUE" argument, but this uses

"cuts=..." (which is usually chosen very high for my plots. I guess

cuts=99 is the best you can do (?)) for plotting the contour lines.

Furthermore, I do not like the numbering of the contour lines this

way. Therefore, I tried to add a standard contour plot. There are 2

problems to do this. First, as I would like to have the levelplot

with a colorkey, the contour lines are plotted over the colorkey (see

example code below). I could not fix this problem by changing the

aspect argument of the levelplot call or by working with xlim and

ylim in the contour plot function. Second, I am not sure if the

contour lines added this way actually represent the points they

should (e.g. does the contour line labeled with 0.5 really hit the

points of this height?). So, is there a simple way of how to add the

contour lines (of the contour function) to the levelplot this way? If

not, is it possible to plot the levelplot with cuts=99 but only draw

the contour lines (with the option "contour=TRUE" in the levelplot

call) at specified points? Is it possible to tell the levelplot

function (with cuts=99) to plot a specified number of contour lines

(say, only to plot 10 contour lines in the whole existing range of z-

values)?

Thank you very much in advance

Marius

[hidden email]
example code:

remove(list=objects())

x.1<-rep(seq(0,1,by=0.04),each=26)

x.2 <- 0.04*(0:25)

y.1<-rep(x.2,26)

y.2 <- 0.04*(0:25)

z.1 <-x.1*y.1

z.2<- matrix(unlist(z.1),ncol=26,byrow=TRUE)

library(lattice) #for trellis-like graphical plots

plot.new()

levelplot(z.1~x.1*y.1,xlim=c(0,1),ylim=c(0,1),aspect=1,scales=list

(relation="free",tick.number=6),cuts=99,colorkey=list(tick.number=6))

contour(x.2,y.2,z.2,levels=seq(0,1,by=0.1),add=TRUE,col="black")

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