[R] Filling polygons with points

Petr Pikal petr.pikal at precheza.cz
Thu Oct 14 16:37:28 CEST 2004



On 14 Oct 2004 at 10:00, Duncan Murdoch wrote:

> On Thu, 14 Oct 2004 15:16:30 +0200, "Wolf, Michael"
> <Michael.Wolf at bezreg-muenster.nrw.de> wrote :
> 
> >Dear list,
> >
> >are there any possibilities to fill a polygon with a point pattern or
> >with a symbol pattern like '+' oder '-' instead of shading lines?
> 
> I don't think the graphics devices know how to do that, but you could
> program it yourself:
> 
> Supposed interior(x,y) is a function that determines whether the
> points (x,y) are in the polygon, then just create a grid of locations,
> subset when interior(x,y) is true, and plot using pch='+'.
> 
> I made a quick search and was unable to find a general implementation
> of the "interior" function for an arbitrary polygon; I'm a bit
> surprised about that.  Hopefully someone else can point to one,

Hi

I think that you can find such functionity in splancs package 
probably function pip() find if points are inside or outside of the 
polygon.

Cheers
Petr



> otherwise please write one, and document it and contribute it to R.
> It's a relatively standard algorithm, and would be useful.
> 
> Duncan Murdoch
> 
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Petr Pikal
petr.pikal at precheza.cz




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