Fri, 18/04/2008 - 17:24 — jonathanm
The Initialisation symbol is used to specify the initial number of individuals in a population submodel.
The Initialisation symbol only has meaning in the context of a population submodel. Therefore, it makes sense to construct a population submodel first, then add the Initialisation to it. This is not strictly necessary: you can add the Initialisation first, then construct a submodel around it, then make the submodel into a population submodel, but it is better practice to construct the population submodel first.
So, assuming that you already have a population submodel in your model diagram:
- You can have a maximum of one Initialisation symbol in any one population submodel. It does not make sense to have more than one, since Simile would then not know which one to use.
- You do not need to have an Initialisation symbol in a population submodel. If you do not have one, then the initial number of instances for the population is zero. You would then have to have a migration symbol if you wanted your population ever to have any instances. (If you only had a reproduction symbol, then the population would never be able to get going, since reproduction only works for individuals already in the population.)
- The Initialisation symbol may receive influence arrows, but (usually) only from variables calculated at the start of the simulation run, whose values do not change. A typical application would be to initialise the number of instances in the population from some fixed environmental attribute, such as the soil type or the area of the system being modelled.
- Although it is possible to draw an influence arrow from the migration symbol to another element, the only use of this is with the channel_is( ) function. The value of the migration symbol is not the value entered or calculated.
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