R help - Oct 2006 - Worm distribution :-)

You are talking about random point patterns, since the glow-worms
appear as ``stars'' (= points).   See the package ``spatial''
(which
comes with R) and try simulating a pattern using Strauss().

Or install the package ``spatstat'' from CRAN --- in this package
there is a variety of ways to simulate ``regular'' random point
patterns --- rMaternI, rMaternII, rSSI, and rmh (which simulates
several point pattern models depending on the specified Papangelou
conditional intensity function).

			cheers,

				Rolf Turner
				rolf at math.unb.ca

Jim Lemon wrote (in response to a question from Alberto Monteiro):
> I once had to do this to generate "random dot stereograms" for
> perception experiments. One easy way is to build from one corner or
> edge (almost all these are rectangular, you can just clip out the
> figure you want later). The user defines a "hit" area for each
> successive point that contains the minimum and maximum allowable
> distances from the two nearest points (typically a small square).
> Points can be generated with two uniform random numbers having a mean
> of the distance to the center of the "hit" area and a range
spanning
> the "hit" square. It was easy to churn out constrained random dot
> patterns on the fly with this method.
	This appears to be:

	(a) closely related to the ideas of ``partially ordered
	Markov models'' developed by Noel Cressie et al (see, e.g.
	Cressie, N., Zhu, J., Baddeley, A. J., and Nair, M. G.
	Directed Markov point processes as limits of partially
	ordered Markov models. Methodology and Computing in Applied
	Probability, 2, 5-21).

	(b) re-invention of the wheel.  As I pointed out in a
	previous posting to the list there are a brazillion ways of
	generating point patterns with interpoint inhibition, readily
	available in R.

				cheers,

					Rolf Turner
					rolf at math.unb.ca