thanks. It really interesting stuff you and your team are into. I'll follow you closely.
Reg. 2) below (Netlogo implementation), I'm really only interested to see how you made your way through to agents' follow the network, and make (random) choices at nodes - in spite of NetLogo's GIS extensions' lack of topology (just to prove that I'm still in my infancy, NetLogo-wise). As you note the algorithms behind are quite easy to follow. It is actually a simple technical matter, I'm pursuing :-)
Hans
>>> Bin Jiang <
[log in to unmask]> 17-11-2009 19:27 >>>
Hans, See my comments below.
> HSP>>> Sure the sw is inessential for the present application. I was
> only curious know if you had managed to program ABM capabilities into
> ArcGIS (which as far as I know only has the shallow
> 'AgtenAnalyst/Repast' package this far) or how far you have managed to
> take NetLogo in terms of networks (which in its GIS-extension dosen't
> facilitate network representation/analysis.
In fact we have implemented car-car interaction and car-street
interaction in both ArcGIS and NetLogo. They are pretty straightforward.
>
> > 2) Is the NetLogo model-code you used for agents interaction with the
> > network publicly available?
> Yes.
> HSP>>> How can I get my hands on it?
We consider to put it publicly once the paper is published. However,
algorithms are clearly described in the paper.
> HSP>>> I appears that you have three 'sets' of information: Real-world
> counts (Taxies in London), network metrics, and agent-simulations. A
> main motivation - as per you introduction - is to investigate which
> networks metric (classic SS + two Rank-based) explains the actual - or
> simulated - traffic flows best. The conclusion is rightfully that the
> flow to a high extent can be explained by means of metrics. Since
> simulated and actual flows are correlated, this means that metrics can
> be used as proxies for (relative) flow patterns (parameter estimates
> can be used to 'upscale' metric indicators to real-world flows).
> Accordingly, this can (if you are putting your glasses in the right
> (or wrong) angle) be read as there's no need for all the fuzz of
> setting up an ABM if flow patterns is the ultimate goal any way.
yes, now I am with you. Simply traffic flow can be predicted by the
metrics.
> HSP>>> I was just wondering if you could elaborate on why ABM are
> needed (which I of course see that they are) in spite of our access to
> such powerful indicators - based on metrics - of flow..
ok, see your point, to setup a "would-be" world which you can experiment on.
> HSP>>> As I see it, the physical environment (in particular the
> network) is the scene on which humans (and other agents) act. The
> environment doesn't predict or dictate. By means of better descriptors
> of the environment - for instance network metrics - we can describe
> the 'scene' (e.g. in terms of 'background' or 'average flows') of our
> agents and thereby make more realistic simulations of the few,
> detailed behaviours in focus. The study of such indicators - like
> yours - is of course of great interest in this respect.
Certainly the simulations can be refined as you suggested.
Thanks and cheers.
Bin
--
--------------------------------------------------------
Bin Jiang
Division of Geomatics, KTH Research School
Department of Technology and Built Environment
University of Gävle, SE-801 76 Gävle, Sweden
Phone: +46-26-64 8901 Fax: +46-26-64 8828
Email:
[log in to unmask] Web:
http://fromto.hig.se/~bjg/--------------------------------------------------------
European Associate Editor
Computers, Environment and Urban Systems: An International Journal
NordGISci:
http://fromto.hig.se/~bjg/NordGISci/ICA Commission:
http://fromto.hig.se/~bjg/ica/
