如何在fill.contour顶部叠加线图？

Question

I'm trying to put a line plot on top of a filled.contour to achieve a similar effect to the one depicted in Figure 1 here .

require("lattice")
require("latticeExtra")

mat = matrix(c(1:9),nrow=3,byrow=TRUE); time = c(1:3); mid = c(1:3)
mat
     [,1] [,2] [,3]
[1,]    1    2    3
[2,]    4    5    6
[3,]    7    8    9

line = colMeans(mat)

shades = colorRampPalette(c("red", "green"))
filled.contour(mid,time,t(apply(mat,2,rev)),
                 zlim=c(1,9),nlevels=9,col=shades(9)) 
xyplot(line~time,type="l")

The most obvious way to go is using layers, but it hasn't worked for me so far.

layer(filled.contour(mid,time,t(apply(mat,2,rev)),
                 zlim=c(1,9),nlevels=9,col=shades(9))) +     
layer(xyplot(line~time,type="l"))

Any suggestions?

Answer 1

Looking at the help page for filled.contour , you may read under "Note": If you want to annotate the main contour plot, for example to add points, you can specify graphics commands in the plot.axes argument.

### your code
require("lattice")
require("latticeExtra")

mat = matrix(c(1:9),nrow=3,byrow=TRUE)
time = c(1:3) 
mid = c(1:3)
line = colMeans(mat)

shades = colorRampPalette(c("red", "green"))

### call to filled.contour with plot.axes{} for some line
filled.contour(mid, time, t(apply(mat, 2, rev)),
           zlim = c(1, 9), nlevels = 9, col = shades(9),
           plot.axes = { axis(1); axis(2); lines(c(1.5,2, 2.5), c(2,2.8, 2.8), col = "white") }
) 

The code yields this plot:

You could also plot the relation between your objects line and time with the following code. Remark that I had to substract 3 from line to make it fit in the graph:

filled.contour(mid, time, t(apply(mat, 2, rev)),
               zlim = c(1, 9), nlevels = 9, col = shades(9),
               plot.axes = { axis(1); axis(2); lines(line-3, time, col = "white") }
) 

yielding the graph below:

Please let me know whether this is what you want.