[R-sig-eco] 2-way adonis (PERMANOVA) incl interaction - how to test for main effects?

[Ellen Pape]

Hi,

Yes, but is there no way of testing for the main effects and interaction
simultaneously?

I also thought of first testing the interaction: adonis2(speciesdataset~ A
*** B, by="margin") , and then - if the interaction is not significant-
testing for the main effects by adonis2(speciesdataset~ A *+* B,
by="margin") . Is this "allowed"?

Thanks,
Ellen

On Tue, 16 Oct 2018 at 12:01, Marcelino De La Cruz Rot <
marcelino.delacruz using urjc.es> wrote:

> El 16/10/2018 a las 11:51, Ellen Pape escribió:
> > Hi all,
> >
> Maybe adonis2(speciesdataset~ A + B, by="margin") ?
>
>
>
> > I don't know whether this is the correct mailing group to address this
> > question:
> >
> > I would like to perform a 2-way permanova analysis in R (using adonis in
> > vegan). By default you are performing sequential tests (by="terms"), so
> > when you have 2 or more factors, the order of these factors matter.
> > However, since I wanted to circumvent this, I chose for the option
> > by="margin" (adonis2(speciesdataset~A*B, by="margin")) but then only the
> > effect of the interaction is tested. On the "help page" of anova. cca it
> > says: "if you select by="margin" -> the current function only evaluates
> > marginal terms. It will, for instance, ignore main effects that are
> > included in interaction terms."
> >
> >
> > My question now is: can I somehow get the main effects tested anyhow,
> when
> > the interaction term is not significant?
> >
> > Thanks,
> > Ellen
> >
> >       [[alternative HTML version deleted]]
> >
> > _______________________________________________
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> > R-sig-ecology using r-project.org
> > https://stat.ethz.ch/mailman/listinfo/r-sig-ecology
> > .
> >
>
> --
> Marcelino de la Cruz Rot
> Depto. de Biología y Geología
> Física y Química Inorgánica
> Universidad Rey Juan Carlos
> Móstoles España
>
>

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