R help - Apr 2010 - xyplot ontop a contourplot (package: lattice)

Hello,

I have a contourplot plot that shows the data I want. However, I would
like to point a certain amount of points from this plot via a
xyplot().

Example:

x <- seq(pi/4, 5 * pi, length.out = 100)
y <- seq(pi/4, 5 * pi, length.out = 100)
r <- as.vector(sqrt(outer(x^2, y^2, "+")))
grid <- expand.grid(x=x, y=y)
grid$z <- cos(r^2) * exp(-r/(pi^3))
levelplot(z~x*y, grid, cuts = 50, panel.xyplot(x~y))


But the point does not show up. What is the correct way to achieve
this?

On 2010-04-16 7:43, Jay wrote:
> Hello,
>
> I have a contourplot plot that shows the data I want. However, I would
> like to point a certain amount of points from this plot via a
> xyplot().
>
> Example:
>
> x<- seq(pi/4, 5 * pi, length.out = 100)
> y<- seq(pi/4, 5 * pi, length.out = 100)
> r<- as.vector(sqrt(outer(x^2, y^2, "+")))
> grid<- expand.grid(x=x, y=y)
> grid$z<- cos(r^2) * exp(-r/(pi^3))
> levelplot(z~x*y, grid, cuts = 50, panel.xyplot(x~y))
>
>
> But the point does not show up. What is the correct way to achieve
> this?
>
Try something like this:

  levelplot(z ~ x * y, grid, cuts = 50,
    panel = function(x, y, z, ...){
       panel.levelplot(x, y, z, ...)
       panel.points(x = c(5, 9), y = c(3, 12),
          cex = 3, pch = 20, col = "red", ...)
       }
  )

  -Peter Ehlers
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>
-- 
Peter Ehlers
University of Calgary