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danlwarren / ENMTools

ENMTools R Package
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documentation for raster.breadth #225

Closed plantarum closed 2 years ago

plantarum commented 2 years ago

The documentation for raster.breadth includes the description:

Description:

     This function measures the spatial heterogeneity of the
     distribution of suitability scores from an ENM.  It returns
     Levins' two metrics of niche breadth.

...

Value:

     results A vector containing the two metrics B1 and B2 for niche
     breadth.

I think this refers to Levins (1968)? Could you add that reference to the help page, and maybe include the formulas as well?

$\text{log } B = - \sum p_i \text{ log } p_i$

$1/B = \sum p_i^2$

Levins, R. 1968. Evolution in changing environments: some theoretical explorations. Princeton University Press.

danlwarren commented 2 years ago

Done, thanks for the suggestions!