R help - Nov 2010 - "negative alpha" or custom gradient colors of data dots in scatterplot ?

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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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 ?
> --
> View this message in context:
http://r.789695.n4.nabble.com/negative-alpha-or-custom-gradient-colors-of-data-dots-in-scatterplot-tp3052394p3052394.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
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> PLEASE do read the posting guide
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> and provide commented, minimal, self-contained, reproducible code.
>


-- 
Ista Zahn
Graduate student
University of Rochester
Department of Clinical and Social Psychology
http://yourpsyche.org