how to specify trophic discrimination factor in tRophicPosition R

[Westrelin Samuel]

Hi all,

 

I forward you two questions I just posted on stackoverflow.

 

In https://cran.r-project.org/web/packages/tRophicPosition/vignettes/Short_guide_to_tRophicPosition.html, it is written :

"An essential component of the model to estimate trophic position is the trophic discrimination factor (TDF). By default the function loadIsotopeData() returns ΔN (3.4 ± 0.98 sd) and ΔC (0.39 ± 1.3 sd) based on Post’s (2002) assumptions. But you can change this assumption to use any values, simply adding them as arguments within the call to this function."

The deltaN and deltaC arguments can indeed be fed with a list of values for these TDF. But instead of a list of values, is it possible to input mean and sd, as these are often given in the literature instead of a list of raw values ?

 

By the way, I have another question : when we run multiSpeciesTP with two Baselines, is alpha forced to be in [0;1] range (as for me it could be theoretcially be out odf this range, at least if it is the same alpha as the one in the formula from Post 2002 paper in Ecology) ?

 

I thank you very luch

Cheers,

Samuel

 

 

Samuel WESTRELIN

samuel.w...@inrae.fr

 

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