[Biomod-commits] contribution of each algorithm to the ensemble

Robin Engler robin.engler at gmail.com
Sat Dec 17 02:50:37 CET 2011

Hi Frederico,

> I’m trying to understand which is the contribution of each of the algorithms
> to the final ensemble. I’ve selected them by using the qual.th, and weighted
> them using weight.method and decay in a “global ensemble” (with all the
> algorithms).

The contributions of each algorithm depend on the type of "ensemble
forecasting" method that you chose, but generally they will be based
on either the AUC or the TSS (or Kappa) scores of each model. In the
case of AUC values, the actual weight used in the ensemble forecast is
the AUC value stretched between 0 and 1 (rather than 0.5 to 1 which is
the original scale of the AUC).

> Is there any way to get a table with the contribution of each of the
> algorithms?

So if you wish to see the contributions of the different models, you
should look at the tables

If you have implemented split-sampling evaulation, then the
AUC/TSS/Kappa values used as weights in the ensemble forecast are
those from the split-sample evaluation. If you have used completely
independent data for evaluation, then the evaluations scores derived
from these data are used.

qual.th is the threshold under which a model is discarded from the
ensemble forecast. Set this value to 0 (or 0.5 if using AUC) if you
wish to keep all models regardless of their evaluation scores.

Hope this helps,

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