[R-meta] Unimodal relationship?

[Cesar Terrer Moreno]

Dear all,

I initially run a model selection analysis, and found 3 potentially important predictors: MAT, MAP and deltaCO2, and potentially also the interaction MAT:deltaco2: https://www.dropbox.com/s/qeu50krq2e78sju/Rplot11.jpeg?dl=0 <https://www.dropbox.com/s/qeu50krq2e78sju/Rplot11.jpeg?dl=0>

However, I suspect that the next predictor in importance, CNr, might be more important than here shown. The problem is that it may follow a nonlinear behaviour. In particular, based on the plot, it seems it may follow an unimodal relationship: https://www.dropbox.com/s/ahpq07y8929muti/Rplot13.jpeg?dl=0 <https://www.dropbox.com/s/ahpq07y8929muti/Rplot13.jpeg?dl=0> or at least interact with other predictors more clearly.

How would you include a potentially unimodal shape in a model in `metafor`?

This is the best model:

rma(es, var, data=dat , mods= ~ 1 + MAT + MAP + deltaco2 + deltaco2:MAT, knha=TRUE))

Please help me figure out how to include CNr in this model as a nonlinear relationship.
Thanks
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