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!
count data
2 messages · Sacha Viquerat, 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 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-help-bounces at r-project.org [mailto:r-help-bounces at 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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