[R-sig-eco] Understanding the output from lme anova

[ONKELINX, Thierry]

Dear Peter,

A * B is just a shorthand notation for A + B + A:B The model will
auto-expand those term to the ":" notation.

Best regards,

Thierry

PS Creating the factors in your dataset and the use of spaces will
increase the readability of your code!

------------------------------------------------------------------------
----
ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek
team Biometrie & Kwaliteitszorg
Gaverstraat 4
9500 Geraardsbergen
Belgium

Research Institute for Nature and Forest
team Biometrics & Quality Assurance
Gaverstraat 4
9500 Geraardsbergen
Belgium

tel. + 32 54/436 185
Thierry.Onkelinx at inbo.be
www.inbo.be

To call in the statistician after the experiment is done may be no more
than asking him to perform a post-mortem examination: he may be able to
say what the experiment died of.
~ Sir Ronald Aylmer Fisher

The plural of anecdote is not data.
~ Roger Brinner

The combination of some data and an aching desire for an answer does not
ensure that a reasonable answer can be extracted from a given body of
data.
~ John Tukey
  

> -----Oorspronkelijk bericht-----
> Van: r-sig-ecology-bounces at r-project.org 
> [mailto:r-sig-ecology-bounces at r-project.org] Namens Hedberg Peter
> Verzonden: maandag 6 december 2010 15:46
> Aan: r-sig-ecology at r-project.org
> Onderwerp: [R-sig-eco] Understanding the output from lme anova
> 
> Dear all.
> 
> I have a question regarding how to interpret the output from 
> my lme.anova.
> 
> My model looks like this
> 
> lme_Cyperaceae<-lme(Cyperaceae~Site+Ditch_block+Tree_cut+as.fa
> ctor(Dist_start)+((as.factor(Dist_start))*Tree_cut)+((as.facto
> r(Dist_ditch))/Ditch_block),random=~1|Mainplot/Transect/Obsplot)
> 
> My question concerns that I use the divission sign to 
> indicate nesting in ((as.factor(Dist_ditch))/Ditch_block), 
> and I use * to indicate two-way interaction in 
> ((as.factor(Dist_start))*Tree_cut), but in the output both 
> terms are presented with a colon (:) sign.
> 
> Tree_cut:as.factor(Dist_start)        3     6  0.259899  0.8520
> Ditch_block:as.factor(Dist_ditch)     4    56  2.695738  0.0399
> 
> Is there something wrong in how I wrote the model, or is the 
> colon sign  used for all interactions weather nested or the * type.
> 
> Would be greatly thankful for any help in understanding this.
> 
> The output mentioned above is from an analysis of lme.anova 
> on the result of the lme model.
> 
> Best regards,
> 
> Petter Hedberg
> 
> 
> 
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