[R] "negative alpha" or custom gradient colors of data dots in scatterplot ?

[Ista Zahn]

Hi,
I suggest taking a look at the plotting functions in the ggplot2
package. For example:


x <- rnorm(10000)
y <- x+rnorm(10000)
dat <- data.frame(x,y)

library(ggplot2)

p <- ggplot(dat, aes(x=x, y=y))
p + geom_point() # too much overplotting: compare to
dev.new()
p + geom_hex(binwidth=c(.1,.1))

Best,
Ista

On Sun, Nov 21, 2010 at 9:13 AM, madr <madrazel at interia.pl> wrote:
>
> I know that by setting alpha to for example col = rgb(0, 0, 0, 0.1) it is
> possible to see how many overlapping is in the plot. But disadvantage of it
> is that single points are barely visible on the background. So I wonder if
> there is possible to make setting that single points would be almost black,
> but with more and more data on the same spot it would get more and more
> whiteish. Or maybe it is possible to make sole data points black but
> overlapped tending to some particular color of choice ?
> --
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-- 
Ista Zahn
Graduate student
University of Rochester
Department of Clinical and Social Psychology
http://yourpsyche.org