[R] is it possible to fill with a color or transparency gradient?

From: Eric Harley <ericctharley_at_gmail.com>
Date: Fri 06 Oct 2006 - 20:15:11 GMT

Hi all,

Is there a way to fill a rectangle or polygon with a color and/or transparency gradient? This would be extremely useful for me in terms of adding some additional information to some plots I'm making, especially if I could define the gradient on my own by putting functions into rgb something like rgb( r=f(x,y), g=f(x,y), b=f(x,y), alpha=f(x,y) ). Not so important whether the coordinates are in terms of the plot axes or normalized to the polygon itself somehow. Ideally it would work not only for a fill color but also for shading lines.

I haven't been using R very long, so it's possible that I'm just missing something, but I haven't found anything like this in the help files. I've tried to poke around in graphics, grid, and ggplot, without any luck so far. I really like some of the functionality in ggplot, and it does some nice things with continuous gradients for the color of scatter plot points, for example, but it each individual point (or grob) is always one solid color as far as I can tell.


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