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On Fri, Apr 16, 2010 at 3:02 PM, Dan Bron <[email protected]> wrote:
> ...
> Can someone give me a short piece of code that will allow me to plot
> polygons (represented by an Nx2 array of numbers) on a graph?
> Ideally, I could pass in multiple polygons (a vector of boxes, each box
> containing a polygon), and have them plotted simultaneously.
>
> This will make it easier to test my models.
>
> -Dan
>
> -----Original Message-----
> From: [email protected] [mailto:
> [email protected]] On Behalf Of Henry Rich
> Sent: Friday, April 16, 2010 2:42 PM
> To: Programming forum
> Subject: Re: [Jprogramming] Polygon containment
>
> Boyko has the right questions here, and I would add only that the devil
> is in the details on this problem, at least in some applications. One
> application is when the polygons tessellate a surface, and you are
> trying to figure out which polygon a point is in. Then you need to make
> sure that your calculation
>
> 0) handles a point that is exactly on an edge, and tests 'inside' for
> one of the polygons sharing the edge, and 'outside' for the other;
>
> 1) handles a point that is exactly on a vertex, as the application needs.
>
> 2) handles degenerate polygons, especially ones that represent a
> non-connected region by having two identical edges in opposite directions.
>
> In addition, it might be important that the algorithm produce the same
> results when the points and polygons are all translated; and you need to
> decide what to do about ill-formed polygons.
>
> The precision issues arising in this calculation are not easy, and in
> some cases the underlying representation of the surface is chosen with a
> view toward making these calculations robust.
>
> Henry Rich
>
>
> Boyko Bantchev wrote:
> > On 16 April 2010 18:01, Dan Bron <[email protected]> wrote:
> >> (2) .............
> >> the maximum inscribed rectangle in that polygon.
> >
> > Dan,
> >
> > This is much harder than finding whether a point is within a
> > polygon. Also, what does it mean a `maximum' rectangle?
> > With respect to its area? In any case, the solution is not
> > unique and probably not very useful.
> >
> >> (3) ................. The inputs is the
> >> polygon and the points, and the output is a boolean
> >> per point, which indicates whether the point is
> >> "truly" in the polygon .............
> >
> > Do points on the polygon's boundary count as in or out?
> >
> > Do you assume that the polygon is non-intersecting?
> >
> > Regards,
> > Boyko
> > ----------------------------------------------------------------------
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> ----------------------------------------------------------------------
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>
--
Devon McCormick, CFA
^me^ at acm.
org is my
preferred e-mail
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