[R-sig-eco] Differences between total constrained inertia (rda) and variance explained (varpart()) in vegan

[Tim Richter-Heitmann]

Yes, you are right.
Thank you very much.

Tim

On 02.11.2015 15:08, Jari Oksanen wrote:
> Probaby the difference is the adjustment: varpart() uses adjusted R-squared, but rda() output reports unadjusted proportions. RsqureAdj() function gives both.
>
> Cheers, jari Oksanen
> ________________________________________
> From: R-sig-ecology <r-sig-ecology-bounces at r-project.org> on behalf of Tim Richter-Heitmann <trichter at uni-bremen.de>
> Sent: 02 November 2015 15:58
> To: r-sig-ecology at r-project.org
> Subject: [R-sig-eco] Differences between total constrained inertia (rda) and variance explained (varpart()) in vegan
>
> Dear list,
>
> when i perform RDA on a species set constrained with a set of
> predictors, which i have tested for their relevance by forward
> selection, i get values for inertia:
>
> Inertia Proportion Rank
> Total         0.12626    1.00000
> Constrained   0.05493    0.43507   11
> Unconstrained 0.07133    0.56493   48
>
> So, the amount of explained inertia is
> 0.05493/0.1262
>
> or roughly 43%.
>
> I am now grouping the same predictors into three groups (soil,
> vegetation, space) and perform varpart() on them, i
> get a total variance (sum of all explained variance) explained of only
> 30%. This has been consistent for me in a variety of datasets.
> Can somebody explain to me the difference?
>
> Thank you!
>
>
> --
> Tim Richter-Heitmann (M.Sc.)
> PhD Candidate
>
>
>
> International Max-Planck Research School for Marine Microbiology
> University of Bremen
> Microbial Ecophysiology Group (AG Friedrich)
> FB02 - Biologie/Chemie
> Leobener Straße (NW2 A2130)
> D-28359 Bremen
> Tel.: 0049(0)421 218-63062
> Fax: 0049(0)421 218-63069
>
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-- 
Tim Richter-Heitmann (M.Sc.)
PhD Candidate



International Max-Planck Research School for Marine Microbiology
University of Bremen
Microbial Ecophysiology Group (AG Friedrich)
FB02 - Biologie/Chemie
Leobener Straße (NW2 A2130)
D-28359 Bremen
Tel.: 0049(0)421 218-63062
Fax: 0049(0)421 218-63069