Monthly Archives: February 2014

A note on calibrating the Neighbourhood Effect (N)

The strength of the Neighbourhood effect (N) depends on the values given to the weights in the matrix that is applied to the land use map with the focal command (see Neighbourhood Dynamics). Clearly, if the weight values applied to N are many times higher than the values that are computed in the Accessibility (A) and Suitability (S) maps, then N will be much stronger that A or S. But in some situations this might not be realistic. For example, if we replace
w <- matrix(c(0,0,50,0,0,0,50,50,50,0,50,50,500,50,50,0,50,50,50,0,0,0,50,0,0), nr=5,nc=5)

with:

w <- matrix(c(0,0,0.5,0,0,0,0.5,0.5,0.5,0,0.5,0.5,5,0.5,0.5,0,0.5,0.5,0.5,0,0,0,0.5,0,0), nr=5,nc=5)

The other parameters (e.g. accessibility, suitability and randomness) play a much larger part in determining the areas that are most likely to change. In this case, it makes for a much more realistic simulation. Compare:

strongN weakN

At left, neighbourhood rules as normal. At right, neighbourhood rules adjusted downwards by a factor of 100.

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SIMLANDER v.1.0.2 – Model updated and Improved february 2014

I’ve prepared an updated version of the model which runs much faster than before (about 10 minutes to complete, instead of 20). Thanks very much to Dr Graeme Hill for the improvements to the code.

The coding for the stochastic parameter also made very little sense. I’ve updated that too. The new code is posted on the script page and updated elsewhere too. The next task is to get the model running for multiple land uses. We’ll see how we get on!