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

From: Jim Lemon <>
Date: Sun 08 Oct 2006 - 23:51:18 GMT

Eric Harley wrote:
> 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.
Hi Eric,

You can fill a rectangle with a "gradient" (slices of colors) using gradient.rect in the plotrix package. Filling an arbitrary polygon would be a lot harder to program. You may also be interested in the color.scale function that assigns colors to numerical values.

Jim mailing list PLEASE do read the posting guide and provide commented, minimal, self-contained, reproducible code. Received on Sun Oct 08 19:55:55 2006

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