question regarding the AICcmodavg package

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question regarding the AICcmodavg package

Hannah van Noort
Dear moderator,

If possible I would like to send in the following question for R-help:

I am analyzing a small data set using PGLS with phylogenetic uncertainty
taken into account and thereby including 100 potential phylogenetic tree
scenarios. I've managed to run models on all of the different trees and
performed model averaging to get parameter estimates for the intercept and
most of the predictor variable slopes using the *AICcmodavg* package and
*APE*, but I seem to get stuck with some of the variables that are also
included in a two-way interaction in the model. I can obtain values for the
two-way interaction but not for the variables separately.

The error I receive is:

“Error in modavg.AICgls(parm = "agefirstbreed", cand.set = Cand.models4, :

Some models include more than one instance of the parameter of interest.
This may be due to the presence of interaction/polynomial terms, or
variables with similar names: see "?modavg" for details on variable
specification and "exclude" argument”



I'm familiar with the *exclude* function of the *AICcmodavg* package, but
this only works when different models have been specified including ones
without these specific two-way interactions and my models are all similar
with regards to the interactions, only the phylogenetic tree scenarios
differ.



I was wondering if there is another method to obtain these averaged
parameter estimates for the concerning predictor variable slopes? Not
excluding the (significant) two-way interaction in which they are also
involved?
Thank you in advance for your reply.

Kind regards,

Hannah van Noort

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Re: question regarding the AICcmodavg package

Cade, Brian
Do not model average the regression coefficients.  This makes no sense (see
Cade 2015.  Model averaging and muddled multimodel inferences).  And, no
there is no reasonable way to model average regression coefficients ala
Burnham and Anderson approach when some of your models include interactions
among predictors and some don't.  Stick to model averaging the predicted
responses and you can do something that is sensible and that can be applied
to any combination of predictor variables including those with interactions.

Brian Cade

Brian S. Cade, PhD

U. S. Geological Survey
Fort Collins Science Center
2150 Centre Ave., Bldg. C
Fort Collins, CO  80526-8818

email:  [hidden email] <[hidden email]>
tel:  970 226-9326


On Tue, Feb 20, 2018 at 2:19 PM, Hannah van Noort <[hidden email]>
wrote:

> Dear moderator,
>
> If possible I would like to send in the following question for R-help:
>
> I am analyzing a small data set using PGLS with phylogenetic uncertainty
> taken into account and thereby including 100 potential phylogenetic tree
> scenarios. I've managed to run models on all of the different trees and
> performed model averaging to get parameter estimates for the intercept and
> most of the predictor variable slopes using the *AICcmodavg* package and
> *APE*, but I seem to get stuck with some of the variables that are also
> included in a two-way interaction in the model. I can obtain values for the
> two-way interaction but not for the variables separately.
>
> The error I receive is:
>
> “Error in modavg.AICgls(parm = "agefirstbreed", cand.set = Cand.models4, :
>
> Some models include more than one instance of the parameter of interest.
> This may be due to the presence of interaction/polynomial terms, or
> variables with similar names: see "?modavg" for details on variable
> specification and "exclude" argument”
>
>
>
> I'm familiar with the *exclude* function of the *AICcmodavg* package, but
> this only works when different models have been specified including ones
> without these specific two-way interactions and my models are all similar
> with regards to the interactions, only the phylogenetic tree scenarios
> differ.
>
>
>
> I was wondering if there is another method to obtain these averaged
> parameter estimates for the concerning predictor variable slopes? Not
> excluding the (significant) two-way interaction in which they are also
> involved?
> Thank you in advance for your reply.
>
> Kind regards,
>
> Hannah van Noort
>
>         [[alternative HTML version deleted]]
>
> ______________________________________________
> [hidden email] mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/
> posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
>

        [[alternative HTML version deleted]]

______________________________________________
[hidden email] mailing list -- To UNSUBSCRIBE and more, see
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.