[R] transparent grays?

[Henrique Dallazuanna]

Try this:

with(trees, symbols(Height, Volume, circles=Girth/24, inches=FALSE, fg
= "gray30",
 bg = sapply(apply(rbind(col2rgb(gray(seq(0,1, l = 10)))/255, alpha =
0.5), 2, as.list), do.call, what = rgb)))


On Thu, Mar 31, 2011 at 2:52 PM, Frostygoat <frostygoat at gmail.com> wrote:
> Is there a grayscale equivalent to alpha levels in rgb?
>
> Example:  I have the following to make red transparent circles overlap
> with previously plotted blue symbols.
>
> symbols(x=sites$long,y=sites$lat,circles=log(sites$prop.nem
> +1),add=T,inches=F,bg=rgb(red=1,green=0,blue=0,
> alpha=0.5),fg=rgb(red=1,green=0,blue=0, alpha=0.5))
>
> I'm having a hard time coming up with a grayscale equivalent.
>
> Thanks!
>
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>



-- 
Henrique Dallazuanna
Curitiba-Paraná-Brasil
25° 25' 40" S 49° 16' 22" O