Wednesday, April 18, 2007

Creating Slider bars in Repast

Slider bars (as in the image above) are a easy way to change model parameters of a simulation. Someone asked how to create a Slider Bar within a Repast model, so I thought I would share it. To create one is relatively straight forward. All you need to do is place this piece of code in the setup method:

//creates a slider which has to be an int.
RangePropertyDescriptor pdMovement = new RangePropertyDescriptor("Movement", 0, 1000, 200);

descriptors.put("Movement", pdMovement);

Where “Movement” relates to the “Movement” parameter in the getInitParam method. For example:

String [] initparams = {"PerAgents", "Movement",
return initparams;

Further information on PropertyDescriptors can be found on the Repast Website under "How to Create PropertyDescriptors"

Tuesday, April 17, 2007

CASA at Agenda Setting Workshop on ABM of Complex Spatial Systems

Andrew Hudson-Smith, Mike Batty, Victor Schinazi and Paul Longley from CASA have been attending the NSF/ESRC Agenda Setting Workshop on Agent Based Modelling (ABM) of Complex Spatial Systems in Santa Barbara. Andy has written two posts about the workshop on his blog: Digital Urban. If you are interested in the ABM and where it is heading its worth checking out his posts from Day 1 and Day 2 of the workshop. Its also worth having a look at the position papers of people attending the workshop .

On a side note his blog is worth exploring Digital Urban anyway as it details and provides examples of CASA research in the fields of digital cities and visualisation on the local, regional and global scale.

Wednesday, April 11, 2007


The SIMSEG model is an extension of the Thomas Schellings segregation model. It allows users to explore ethnic diversity in terms of number of groups and the relative sizes of each group, specify ethnic preferences, specify the level of socio-economic inequality within and between ethnic populations and to specify agents preferences for neighbourhood status and housing quality within a cellular space. Neighbourhoods are bounded by larger areas to evaluate neighbourhood ethnic mix and agents can only move to areas where they can afford.

A free trial version of the SimSeg Learning Edition can be downloaded from the website: and the site also provides a useful review article of theoretical perspectives on residential segregation in American urban areas along with other resources.

If you interested in segregation, there are a whole host of other models available on the internet. For example Schelling Segregation Model created by Chris Cook, written is C# (the source code is available), A java applet created by Raj Singh, A NetLogo model or a Repast model created byGirardin et al., (2006) .

Further Reading:

Fossett, M. and Senft, R. (2004), 'SIMSEG and Generative Models: A Typology of Model-Generated Segregation Patterns', Proceedings of the Agent 2004 Conference on Social Dynamics: Interaction, Reflexivity and Emergence, Chicago, USA, pp. 39-78, Available at

Wednesday, April 04, 2007


Joana Simoes, has recently completed a PhD at CASA. Her thesis was on An Agent-Based Approach to Spatial Epidemics through GIS in which she simulated the diffusion of mumps in Portugal in the late 1990s at regional and local level using a SEIR (susceptible- exposed- infected removed) infection model built in a spatial network of small worlds.

The model she created is called EpiSIM written in C++. Two sets of libraries were used to build this software: Qt, for the graphical API and Shapelib for accessing geographic data. Further information can be seen on the project website and on Joana’s personal website.