[R] overlaid filled contour plots

[Michael Friendly]

I'm trying to make a set of contour plots of bivariate kernel density 
estimates, showing three such plots overlaid,
similar to this plot

http://euclid.psych.yorku.ca/SCS/Private/Test/ridge-boot2.pdf

except that I would like to have the contours *filled* (using 
transparent colors).  To make this reproducible, I've
saved the results of KernSmooth::bkde2D() in the following file:

http://euclid.psych.yorku.ca/SCS/Private/Test/bkde2D-boot.RData

 From this, the essence of my plot can be produced by the following:

# show calls to bkde2D()
#library(KernSmooth)
#dest0 <- bkde2D(lbt[,wh], bandwidth=.5, range.x=list(c(-16, 8), c(-5,5)))
#dest1 <- bkde2D(lbt[,1+wh], bandwidth=.5, range.x=list(c(-16, 8), c(-5,5)))
#dest2 <- bkde2D(lbt[,2+wh], bandwidth=.5, range.x=list(c(-16, 8), c(-5,5)))
#save(dest0, dest1, dest2, cm0, cm1, cm2, file="bkde2D-boot.RData")

con <- 
url("http://euclid.psych.yorku.ca/SCS/Private/Test/bkde2D-boot.RData")
## print the value to see what objects were saved.
print(load(con))
close(con)

col <- c("black", rainbow(5, start=.6, end=.1))
clr <- col[c(1,3,6)]

contour(dest0$x1, dest0$x2, dest0$fhat, nlevels=4,
     xlim=c(-8,4), ylim=c(-3,0), cex.lab=1.25,
     xlab="GNP", ylab="Unemployed"     )
contour(dest1$x1, dest1$x2, dest1$fhat, nlevels=4, add=TRUE, col=clr[2])
contour(dest2$x1, dest2$x2, dest2$fhat, nlevels=4, add=TRUE, col=clr[3])
lines(rbind(cm0, cm1, cm2))
points(rbind(cm0, cm1, cm2), col=clr, pch=16, cex=1.5)

I've tried filled.contour(), as below, except that (a) it doesn't allow 
add=TRUE, and (b) has no way to suppress the legend.

# try filled contours, using transparent colors
colramp0 = colorRampPalette(c("white", clr[1]))
col <- paste(colramp0(5), "80", sep="") # make transparent
filled.contour(dest0$x1, dest0$x2, dest0$fhat, nlevels=4,
     xlim=c(-8,4), ylim=c(-3,0), cex.lab=1.25, col=col,
     xlab="GNP", ylab="Unemployed"     )

colramp1 = colorRampPalette(c("white", clr[2]))
col <- paste(colramp1(5), "80", sep="") # make transparent
filled.contour(dest1$x1, dest1$x2, dest1$fhat, nlevels=4,
     xlim=c(-8,4), ylim=c(-3,0), cex.lab=1.25, col=col,
     xlab="GNP", ylab="Unemployed"     )

colramp2 = colorRampPalette(c("white", clr[3]))
col <- paste(colramp2(5), "80", sep="") # make transparent
filled.contour(dest2$x1, dest2$x2, dest2$fhat, nlevels=4,
     xlim=c(-8,4), ylim=c(-3,0), cex.lab=1.25, col=col,
     xlab="GNP", ylab="Unemployed"     )


Note that the structure of the result of bkde2D() is a list of the 
following form, so I think I'm stuck with
plotting the 3 density estimates separately as I do above.

 > str(dest0)
List of 3
  $ x1  : num [1:51] -16 -15.5 -15 -14.6 -14.1 ...
  $ x2  : num [1:51] -5 -4.8 -4.6 -4.4 -4.2 -4 -3.8 -3.6 -3.4 -3.2 ...
  $ fhat: num [1:51, 1:51] 2.08e-04 1.60e-04 5.88e-05 1.08e-05 1.20e-06 ...
 >

Any ideas?

-Michael

-- 
Michael Friendly     Email: friendly AT yorku DOT ca
Professor, Psychology Dept.
York University      Voice: 416 736-5115 x66249 Fax: 416 736-5814
4700 Keele Street    Web:   http://www.datavis.ca
Toronto, ONT  M3J 1P3 CANADA