Re: Simulating Individual Behavior

[Jan Kreft]

Doug,

thanks for your comments. 

Doug Donalson wrote:

> Be careful of this method.  There are at least two
> main problems you can run into.  The first is that you can
> force fit a set of parameters to a model and get a result out 
> that matches some experimental data but you have no guarentee
> that you have any more that a pretty picture.  

The way to avoid such a force fit that I'm thinking about is
optimizing/evolving the parameter set. Suppose that the parameter set is
optimized with respect to the individuals' fitness (one or a few
definitions of fitness or performance could be used). Then you compare the
result of only those sims with optimized params with real data (in my case
lab data, therefore the variation will be better known hopefully). (Real
data also are the result of (evolutionary)  optimized behavior).  If you
don't get a reasonable match the assumptions about the basic mechanism
will be incorrect or lacking important points.

Does this make sense to you? Do you see a better way to get around the
lack of appropriate, not theoretically biased quality data?

Simply setting parameters to experimental values beforehand could get you
into serious problems also if a tiny deviation of a param has a large
effect and it happens that that experimental value is just a bit wrong...

Jan.

> [...]
> If you run a field experiment 20 times you
> will get 20 results and hope that there is enough commonality
> to get statistical power.  Therefore, the result you are
> to which you are callibrating is just a sample from a statistical
> distribution.  If that distribution has a wide varience then you
> may have fine-tuned your model to an point far from the expected
> behavior.  
> 
> A second trap is that if your assumption of the basic mechanisim
> is incorrect you may fine-tune to a different system that has
> the same result for that set of parameters.
> 
> Unfortunatly, I don't has a good set of procedures to eleminate 
> these hazzards.  I am also not saying that this is a bad method,
> it happens to be one I saw abused in an attempt to justify
> the use of a differential equation based mode.
> 
> Doug Donalson



                  ==================================
   Swarm-Modelling is for discussion of Simulation and Modelling techniques
   esp. using Swarm.  For list administration needs (esp. [un]subscribing),
   please send a message to <address@hidden> with "help" in the
   body of the message.
                  ==================================