[R] Draw a circle on a filled.contour() plot

[Renaud Lancelot]

Try levelplot in package lattice instead of filled.contour: you will
be able to annotate the plot using the grid package. Moreover, you can
remove the key using the colorkey argument.

library(lattice)
library(grid)
z <- as.matrix(read.table("hist_2d"))
dimnames(z) <- NULL
Data <- expand.grid(x = seq(-4.45, 4.45, len = 90),
                    y = seq(-4.45, 4.45, len = 90))
Data$z <- c(z)
rm(z)
Cols <- colorRampPalette(c("white", "blue","yellow","red"))
levelplot(z ~ x * y, data = Data,
  aspect = 1, colorkey = FALSE, col.regions = Cols(6),
    panel = function(...){
      panel.levelplot(...)
      grid.circle(x = 0.62, y = 0, r = 2.5, default.units = "native")
      })

Best,

Renaud

2006/12/17, Webmaster <webmaster at citedesjeunes.com>:
> > The output produced by 'filled.contour' is actually a combination
> >      of two plots; one is the filled contour and one is the legend.
> >      Two separate coordinate systems are set up for these two plots,
> >      but they are only used internally - once the function has
> > returned
> >      these coordinate systems are lost.  If you want to annotate the
> >      main contour plot, for example to add points, you can specify
> >      graphics commands in the 'plot.axes' argument.  An example is
> >      given below.
>
> Thanks!
>
> I now have another question (hopefully the last) for which I couldn't
> find an answer in the mailing-list archives: how can I get rid of the
> color key on the contour.filled() plot? I that question, unanswered,
> in a post one year ago on this same list, so I hope it's by any mean
> possible... (I think it's possible to change the code completely and
> use image(), but it's much less pretty).
>
> FX
>
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>


-- 
Renaud LANCELOT
Département Elevage et Médecine Vétérinaire (EMVT) du CIRAD
Directeur adjoint chargé des affaires scientifiques

CIRAD, Animal Production and Veterinary Medicine Department
Deputy director for scientific affairs

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