[Biomod-commits] Comparison among variable importance

Viorel Popescu vioreldpopescu at gmail.com
Thu May 16 16:44:25 CEST 2013

Hi everyone, I had a similar question a few weeks ago, and from my
understanding the varImportance scores are drawn from correlation
coefficients between different models (with and without the respective
variable permuted), namely, 1 minus the correlation (r). Hence, they cannot
add up to 1, the way variable importance is performed in MaxEnt. In that
case, standardizing the scores would not a be very good way to deal
with the varImportance. Am I missing something here?

The way I dealt with them (with advice from Wilfried) was to show boxplots
of varImportance score for each variable across modeling techniques (and
taxa if you need to make such comparisons), and refer to median scores
(distribution of scores was far from normal).


On Thu, May 16, 2013 at 3:39 AM, Damien Georges
<damien.georges2 at gmail.com>wrote:

> Dear Antonio,
> I guess you are right and you need to make  a kind of standardisation of
> scores to make them all comparable. Make them sum to 1 is a good way to do
> it.
> Cheers,
> Damien.
> On 16/05/2013 12:09, Antonio Canepa wrote:
>> Dear list,
>> I would like to know if you can directly compare among different models
>> the
>> variable importance of each variable selected?
>> My guess is not, because when I got the importance of each variable (
>> getModelsVarImport()), the sum of all of them for each model was not = 1.
>> I don't know if I'm doing something wrong or there is another way to
>> "standardise" the output from getModelsVarImport() and thus compare
>> throughout models ?
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Viorel D. Popescu
David H. Smith Conservation Research Fellow
University of California - Santa Cruz &
Simon Fraser University, Biological Sciences
(604) 340 4228

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