[R] Multi response GAM

[Richard O'Keefe]

You might want to start by re-expressing the "amounts"
variables to
  total amount * (relative fish 1, relative fish 2, invertebrates)
and then using the Isometric Log-ratio transformation to
convert the compositional part to orthonormal coordinates.
https://stats.stackexchange.com/questions/259208/how-to-perform-isometric-log-ratio-transformation
may help.

I can't help wondering whether viewing the diet in terms of
the nutrients offered by the different components might yield
more insight.

On Sat, 18 Apr 2020 at 11:00, Tristan Kosciuch
<tristan.kosciuch using mail.mcgill.ca> wrote:
>
> Hello,
>
> I am modelling the diet of Nile perch through time. I have 3 diet classes as
> my response variables; fish 1, fish 2, and invertebrates.
>
> The response variables are correlated, declines in invert consumption ~
> increase in fish consumption. Any advice on how to handle this would be
> appreciated. I would like to use GAMs as my time series shows fluctuations
> that could only be fit by high order polynomials if I were to use a linear
> model, but open to suggestions.
>
> Thank you for your time.
>
> P.s. I will be comparing the fit of the time series GAM with a model based
> on other predictors, with a training and validation split for my data.
>
>
>
> ---
>
> Tristan Kosciuch
>
> Stewart Biology Building, McGill University
>
> 1205 Dr Penfield Ave, Montreal QC H3A 1B1
>
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>
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