Variance Inflation Factors

[Megan S]

Hi all,

When using variance inflation factors to decide which correlated variables to remove from the MaxEnt model, do you run the linear regression separately using each climate variable as the dependent variable (for bioclim, 19 models), remove the variable with the highest VIF out of all these models, then run 18 models, remove the variable with the highest VIF out of all of these, etc. until you have all VIFs below your threshold? 

Thank you so much,

Megan

[Husam El Alqamy]

no You run the regression with all variables first and check for the VIF. then you removel those with the highest VIF and run it again with smaller group of variables and check the outcome again and then remove those with the VIF greater than 10 and run it again with the smaller list of variables until you get a list of all variables with all VIF below 10. then this list of variables that you use in your maxent model. 

Husam El Alqamy

 

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Husam El Alqamy, B.Sc., M.Phil.
Sr. Biodiversity GIS Analyst ,
Environmental Information Sector, EIS
Environmental Agency Abu Dhabi,UAE
Antelope Specialist Group, ASG - IUCN

[Megan S]

Hi Hasam,

Thanks for your reply. What variable do you use as the dependent variable? If it is presence/absence, I think you would want to do a logistic regression rather than linear? I was going to use the number of presences per cell (instead of binary presence/absence) but it looks like MaxEnt only uses the binary information.