Plot as bitmap in PDF

Question

I am currently working on CGH array results, which involve several plots of dozens of thousands of points, and i would like to benefit from the multiple page feature of the

Answer 1

Here's a solution that gets you close (50kb) to your desired file size (25kb), without requiring you to install LaTeX and/or learn Sweave. (Not that either of those are undesirable in the long-run!)

It uses the grid functions grid.cap() and grid.raster(). More details and ideas are in a recent R-Journal article by Paul Murrell (warning : PDF):

require(grid)
# Make the plots
dev.new()  # Reducing width and height of this device will produce smaller raster files
    plot(rnorm(2e4), rnorm(2e4), pch="+", cex=0.6)
    cap1 <- grid.cap()
    plot(rnorm(2e4), rnorm(2e4), pch="+", cex=0.6, col="red")
    cap2 <- grid.cap()
dev.off()

# Write them to a pdf
pdf("test.pdf", onefile=TRUE)
     grid.raster(cap1)
     plot.new()
     grid.raster(cap2)
dev.off()

The resulting pdf images appear to retain more detail than your files test1.png and test2.png, so you could get even closer to your goal by trimming down their resolution.