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- Xref: sparky comp.graphics:9716 comp.graphics.explorer:208 comp.graphics.visualization:1337
- Path: sparky!uunet!munnari.oz.au!uniwa!watson
- From: watson@maths.uwa.oz.au (David Watson)
- Newsgroups: comp.graphics,comp.graphics.explorer,comp.graphics.visualization
- Subject: Re: (Q) calculating spatial density
- Date: 15 Sep 1992 00:21:05 GMT
- Organization: The University of Westrn Australia
- Lines: 29
- Message-ID: <193a9hINNn8l@uniwa.uwa.edu.au>
- References: <vthrc.716467347@brolga>
- NNTP-Posting-Host: madvax.maths.uwa.oz.au
- Keywords: spatial density algorithm statistics
-
- vthrc@brolga.cc.uq.oz.au (Danny Thomas) writes:
-
- >I've got a complex 2D shape with a set of points in it and need to
- >generate a map of density of those points.
-
- A little known but useful technique for density estimates of point sets
- is the inverse of Voronoi neighbourhoods. In general terms, the area
- (volume, etc.) of the Voronoi region about each point is calculated and
- then the inverse of this value constitutes a density measurement at that
- point. When a set of such density measurements are contoured, the surface
- implied by the contouring procedure expresses the density distribution
- function for the point set. Point sets with "holes" will have negligibly
- low densities in the regions of the holes.
-
- This approach is a generalization of the "points within a circle" manual
- method of density estimation in the sense that the area and shape of the
- counting region is adjusted automatically to be the most efficacious
- possible for each subregion.
-
- A commercial program, NNGRIDR, is available that will compute these
- inverse area values and then interpolate with natural neighbour interpolation
- at the nodes of a regular grid suitable for contouring by conventional
- contouring packages. Send email to the under-signed for more details.
-
- --
- Dave Watson Internet: watson@maths.uwa.edu.au
- Department of Mathematics
- The University of Western Australia Tel: (61 9) 380 3359
- Nedlands, WA 6009 Australia. FAX: (61 9) 380 1028
-