clearing plot / over plotting of points
Jochen,
On Apr 30, 2012, at 8:40 AM, jochen laubrock wrote:
Hello, points are not completely erased if overplotted in the background color, using points from base graphics. Instead, they leave a faint grey trace, both if running R.app and R in Terminal. Is this intended?
Yes, you may want to read up on "anti-aliasing". You can disable anti-aliasing (with antialias=F) but you get very ugly plots.
What is the proper way to erase a plot if one does not want to create a new plot, which presumably has some overhead in an animation?
You presume wrongly - it is in fact less efficient to try to erase a plot by painting over it and re-drawing a new one as opposed to drawing a new page, because you keep piling up the display list which forces R to redraw everything including over-painted parts of the plot. If you want to do animation I hope you are aware of the crucial commands dev.hold()/dev.flush() designed for that purpose (and efficiency). Cheers, Simon
Example, using points: A <- matrix(rnorm(1000), 500, 2) plot(range(A), range(A), type="n") points(A) points(A[1:250, 1:2], col="white", bg="white") I'm posting to this list because I have not tested under a different OS. Jochen
sessionInfo()
R version 2.15.0 (2012-03-30)
Platform: x86_64-apple-darwin9.8.0/x86_64 (64-bit)
locale:
[1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8
attached base packages:
[1] stats graphics grDevices utils datasets methods base
other attached packages:
[1] lattice_0.20-6 MASS_7.3-17
loaded via a namespace (and not attached):
[1] grid_2.15.0 tools_2.15.0
PS: Points *are* erased if using image
# using image
A <- matrix(0, 100, 100)
ix <- runif(1000, 0, 10000)
A[ix] <- 1
image(seq(0,1,length=100), seq(0,1,length=100), A, col=c("white", "black"))
A[ix[1:500]] <- 0
image(seq(0,1,length=100), seq(0,1,length=100), A, col=c("white", "black"))
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