[R-sig-Geo] Build hexagonal lattice coverage

[Nicholas Lewin-Koh]

Hi Tim,
If you look in the hexbin code (eeek) you will realize that hexbin just
creates 
a regular latttice of points, and the hexagons are implicit. Actually
the storage is even more compact, the hexagons are integers and
everything
is derived from the limits. The algorithm is explained in the vignette. 
For a regular lattice the topology is very simple, so I don't think it
is really worth storing anything but the hexagon centers.

If you are doing grid like operations on hexagonal lattices, as long
as the lattices are the same, you still don't need the topology. You
could
even store two offset square grids and get the hexagons, provided your
lattice 
is not rotated. You can also look at the package diamonds, Dennis White
may have something
to add, if he is lurking around on the list.

Nicholas


------------------------------------------------------------
> 
> Message: 1
> Date: Fri, 2 Mar 2007 21:52:01 -0600
> From: "Tim Keitt" <tkeitt at gmail.com>
> Subject: [R-sig-Geo] Build hexagonal lattice coverage
> To: r-sig-geo at stat.math.ethz.ch
> Message-ID:
> 	<6262c54c0703021952u35890446m3c0f1eb9a9b85a25 at mail.gmail.com>
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> 
> Hi All,
> 
> I'd like to make a hexagonal lattice (stored in a shapefile, ogr
> coverage or postgis geometry). Is the general approach to make a
> series of independent hexagons and place them in the plane such that
> adjacent edges sit directly on top of each other? Or can one build a
> mesh out of connected line segments? If it is the latter, how does one
> associate a data value with each hexagon in the mesh? I'd like to
> achieve something like the output of the hexbin package, but display
> the result in ArcGIS or QGIS.
> 
> THK
> 
> -- 
> Timothy H. Keitt, University of Texas at Austin
> Contact info and schedule at http://www.keittlab.org/tkeitt/
> Reprints at http://www.keittlab.org/tkeitt/papers/
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> 
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> End of R-sig-Geo Digest, Vol 43, Issue 3
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