[R] adding contour lines to a filled.contour

[Andy Bunn]

Hi all, 

Does anybody know how to add contour lines to a filled contour plot?

I want to draw a single contour around values that are above a certain
level (e.g., significant). The problem I'm having is that since the
filled.contour command actually draws two plots (data and the key),
adding contour lines paints them over both plots.

Any suggestions?

Thanks, Andy


#~~~~~~~~~~~~~~~~~~~
#example

junk.mat <- matrix(rnorm(1600), 16, 100)

filled.contour(junk.mat, 
               color = terrain.colors)

#set values < 2 to zero
contour.mat <- ifelse(junk.mat < 2, 0, junk.mat)

#add contours
contour(contour.mat,
        levels = 1,
        drawlabels = F,
        axes = F, 
        frame.plot = F,
        add = T)