mixed model nested ANOVA
Hi Sebpe, the analysis of the data that you describe could be a complex and lengthy process, in which decisions that you are confronted by are affected by previous decisions that you have made. I recommend obtaining the assistance of a statistician, preferably a local one whose door you can knock on. If you are unable to do so then I suggest that you borrow/buy a copy of the Pinheiro and Bates book, which documents lme() and its friends, and study it carefully, especially the worked examples. Good luck! Andrew
On Fri, Dec 12, 2008 at 03:13:06PM +0000, Sebpe De Smedt wrote:
Hi, I'm working on leaf characteristics of trees. Each tree is characterised by about 10 leaf traits. The trees were sampled at 9 different locations (about 20 to 30 trees/location, NOT balanced), grouped in 3 different climatic zones (Sahelian, Soudanian and Guinean) (NOT balanced). Further, each tree is characterised by some degree of human pressure (mutilation degree), in total 4 different degrees were defined (NOT balanced). In the dryer zones, the trees are under a much higher human pressure than in the more humid climatic zones, "zone" and "mutilation degree" are thus strongly correlated. I want to know how "zones" (fixed effects, climate interests me) and "locations" (nested in "zones", random effects, location doesn't interests me) are influencing the leaf traits (say for example "SLA"). Further, also human pressure is affecting leaf traits so I want to characterise the influence of "mutilation degree" (fixed effects) on "SLA". I found some interesting information, but still, I am not be able to analyse the data properly. I think I have to use the function lme() or lme(). Can anyone tell me which function and command I have to use? And how I can produce an ANOVA table? Thanks in advance, Sebpe De Smedt [[alternative HTML version deleted]]
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Andrew Robinson Department of Mathematics and Statistics Tel: +61-3-8344-6410 University of Melbourne, VIC 3010 Australia Fax: +61-3-8344-4599 http://www.ms.unimelb.edu.au/~andrewpr http://blogs.mbs.edu/fishing-in-the-bay/