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

[Duncan Murdoch]

On 12/17/2006 9:31 AM, Webmaster wrote:
>> 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).

I don't see any option in there, so you might have to write your own 
version to do it.  The source for the regular function is in

http://svn.r-project.org/R/trunk/src/library/graphics/R/filled.contour.R

and the part that plots the key is

     ## Plot the 'plot key' (scale):
     mar <- mar.orig
     mar[4] <- mar[2]
     mar[2] <- 1
     par(mar = mar)
     plot.new()
     plot.window(xlim=c(0,1), ylim=range(levels), xaxs="i", yaxs="i")
     rect(0, levels[-length(levels)], 1, levels[-1], col = col)
     if (missing(key.axes)) {
         if (axes)
             axis(4)
     }
     else key.axes
     box()
     if (!missing(key.title))
	key.title

You'd probably also want to change the layout, because you won't want 
the blank space there.  Or possibly you could get the results you want 
from contour(), which doesn't plot the scale.

Duncan Murdoch