[R] count data

[ONKELINX, Thierry]

Dear Sacha,

Do you revisit the same locations per site? If so, use (1|site/location) as random effect. Otherwise use just (1|site). You might want to add a crossed random effect (1|date) if you can expect an effect of phenology.

Best regards,

Thierry

PS R-sig-mixed-models is a better list for this kind of questions.

----------------------------------------------------------------------------
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 op 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-help-bounces op r-project.org 
> [mailto:r-help-bounces op r-project.org] Namens Sacha Viquerat
> Verzonden: vrijdag 25 februari 2011 13:16
> Aan: r-help
> Onderwerp: [R] count data
> 
> hello dear list! I wonder about the layout of my csv for my 
> study design:
> 
> i have 11 different sites.
> 
> each site had been visited 9 times.
> 
> on each visit, 6 distinctive water parameters had been taken 
> ONCE on each visit (as continuous variables).
> 
> on each visit, the fish abundance was counted using a net at 
> 3 different locations within the site (count data).
> 
> I know i will have to do an lmer using the nested locations 
> as error term. Question is: how to organize my data, since i 
> have abundances from the same 3 locations per site replicate 
> but only one water parameter measurement per site replicate. 
> to give you an idea, heres the basic look so far of my csv:
> 
> 
> site    location    abundance    pH    no3    and so on...
> A    1        12        7.1    0.003    ...
> A    2        15        7.1    0.003    ...
> A    3        18        7.1    0.003    ...
> B    1        11        7.4    0.004    ...
> B    2        8        7.4    0.004    ...
> B    3        17        7.4    0.004    ...
> A    1        13        7.2    0.001    ...
> A    2        19        7.2    0.001    ...
> A    3        21        7.2    0.001    ...
> B    1        9        6.9    0.002    ...
> B    2        5        6.9    0.002    ...
> B    3        2        6.9    0.002    ...
> 
> i just made up the table to give an idea how the data looks 
> like. the goal would be to analyze fish abundance ~ water 
> parameters, does anyone have a suggestion?
> 
> thanks in advance!
> 
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