Category Archives: statistical model

9.1 the difficulty of inferring process from pattern

This is an implementation of the model described in

Cale WG, Henebry GM and Yeakley JA 1989 Inferring process from pattern in natural communities. BioScience, 39, 600-605.

which demonstrates the challenges involved in inferring processes from patterns.

Click on the image to download and save the model NetLogo file. You will need to install NetLogo to run this file.

5.19 the ‘sand-pile’ forest fire model

This model is an implementation of a simple forest fire model with a primary focus on the size distribution of the fires that are produced. It is based on the model described in

Bak P and Chen K 1990 A forest-fire model and some thoughts on turbulence. Physics Letters A, 147, 297–300.

Click on the image to download and save the model NetLogo file. You will need to install NetLogo to run this file.

5.12 Eden growth along a linear invasion front

This model draws on ideas discussed in

Edwards SF and Wilkinson DR 1982 The surface statistics of a granular aggregate. Proceedings of the Royal Society of London. Series A, 381(1780), 17-31.

and allows you to explore the rate of progress made by an Eden invasion process advancing along a linear ‘front’.

Click on the image to download and save the model NetLogo file. You will need to install NetLogo including the gradient extension to run this file.

4.2 demonstration of the correlation length effect in random walks

This model demonstrates how a correlated random walk, when consecutive steps are aggregated, reverts to a simple random walk without correlation but with a longer mean step length. This effect means that correlated random walks are ultimately diffusive (not super-diffusive) like simple random walks.

Click on the image to download and save the model NetLogo file. You will need to install NetLogo to run this file.

4.1 random walks

This model implements a number of variations on the random walk including the lattice-based walk, the simple random walk, walks with different distributions of step lengths, and correlated (direction) random walks.

Two variants are shown in the videos to the right: a simple random walk, and a directionally correlated random walk.

Click on the image to download and save the model NetLogo file. You will need to install NetLogo to run this file.

2.7 the double Thomas point process

This model demonstrates a double Thomas point process where consecutive ‘generations’ of point events originate from the location of ‘parent’ events. Although the process is not intended as a dynamic model, it clearly shows how we can progress from a static to a dynamic model, similar to that of Flügge et al.

Click on the image to download and save the model NetLogo file. You will need to install NetLogo including the gradient extension to run this file.

2.5 a point process with inhibition

This model demonstrates a point process with inhibition which prevents two events from being located nearer one another than some specified distances and can produce evenly-spaced or dispersed patterns.

Click on the image to download and save the model NetLogo file. You will need to install NetLogo including the gradient extension to run this file.