Background
The reference manual for the gbm package
states the interact.gbm
function computes Friedman's H-statistic to assess the strength of variable interactions. the H-statistic is on the scale of [0-1].
The reference manual for the dismo package
does not reference any literature for how the gbm.interactions
function detects and models interactions. Instead it gives a list of general procedures used to detect and model interactions. The dismo
vignette "Boosted Regression Trees for ecological modeling" states that the dismo
package extends functions in the gbm
package.
Question
How does dismo::gbm.interactions
actually detect and model interactions?
Why
I am asking this question because gbm.interactions
in the dismo package
yields results >1, which the gbm package
reference manual says is not possible.
I checked the tar.gz for each of the packages to see if the source code was similar. It is different enough that I cannot determine if these two packages are using the same method to detect and model interactions.