[R] filled plot symbols

[Bill Simpson]

On Tue, 17 Oct 2000 ben at zoo.ufl.edu wrote:

>   As for the wider question of why there are two different kinds of
> points, etc., etc. -- I think this is basically historical, and makes more
> sense if you think about the R graphics model, which is just objects drawn
> onto a canvas. pch=1 doesn't fill in the symbol with any color at all,
> while pch=16 fills it in.  If you want quick access to filled and unfilled
> symbols, having pch 1 and 16 (and all their neighbors) is easier than
> fussing with background colors.  
I don't see the reason for having the unfillable versions of the plot
symbols (1-6). If you do 
plot(x,y,type="o",pch=21)
you get transparent circles and if you do
plot(x,y,type="o",pch=21,bg="white")
you get opaque circles. So no need for pch=1 (which can only do
transparent circles).

In any case, I don't see why anyone would want the transparent symbols. It
makes for a messy plot whenever there is overlap. Occlusion is better than
overlap.

> I don't know how hard it would be to make
> a point type, or a graphics option, that automatically filled points in
> with the plot's background color.

I personally think that would be great! (With the default background
colour being white)

As Ross said another possibility is to use type="b", but I don't like the
large gaps around the symbols. If type="b" produced a plot with snugly
fitting lines (no gaps), that would be fine (and then there would be no
need for type="o").

Bill

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