Re: [R] mixed model nested ANOVA

2008-12-12 Thread Andrew Robinson
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

[R] mixed model nested ANOVA

2008-12-12 Thread Sebpe De Smedt
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, eac

[R] Mixed Model nested ANOVA (lme help)

2008-03-14 Thread Stephen Cole
Hello Again R help readers - I have posted in the past and want to thank all those who replied with helpful suggestions. This regards mixed model anova, and the nlme package. My purpose is to make a comparison of barnacle recruit density from 3 different regions. In each of these regions i have

Re: [R] mixed model nested ANOVA (part two)

2008-02-24 Thread S Ellison
>> Also i have read in Quinn and Keough 2002, design and analysis of >> experiments for >> biologists, that a variance component analysis should only be conducted >> after a rejection >> of the null hypothesis of no variance at that level. Hmmm... This does rather assume that 'no significant resu

Re: [R] mixed model nested ANOVA (part two)

2008-02-24 Thread Mark Difford
Hi Stephen, Slip of the dactylus: lm() does not, of course, take a fixed=arg. So you need To recap: mod.rand <- lme(fixed=y ~ x, random=~x|Site, data=...) mod,fix <- lm(y ~ x, data=...) ## or ##mod,fix <- lm(formula=y ~ x, data=...) Bye. Mark Difford wrote: > > Hi Stephen, > >>> Also

Re: [R] mixed model nested ANOVA (part two)

2008-02-24 Thread Mark Difford
Hi Stephen, >> Also i have read in Quinn and Keough 2002, design and analysis of >> experiments for >> biologists, that a variance component analysis should only be conducted >> after a rejection >> of the null hypothesis of no variance at that level. Once again the caveat: there are experts on

[R] mixed model nested ANOVA (part two)

2008-02-24 Thread Stephen Cole
First of all thank you for the responses. I appreciate the suggestions i have received thus far. Just to reiterate I am trying to analyze a data set that has been collected from a hierarchical sampling design. The model should be a mixed model nested ANOVA. The purpose of my study is to analyz

Re: [R] Mixed model Nested ANOVA

2008-02-22 Thread Rune Haubo
Hi Stephen On 22/02/2008, Stephen Cole <[EMAIL PROTECTED]> wrote: > hello R help > > I am trying to analyze a data set that has been collected from a > hierarchical sampling design. The model should be a mixed model nested > ANOVA. The purpose of my study is to analyze the variability at each

Re: [R] Mixed model Nested ANOVA

2008-02-22 Thread jebyrnes
So, Site is nested in location. Location is nested in Region. And you are looking at how density varies. Let's think about this from the point of view of a model with varying intercepts. You have some mean density in your study. That mean will deviate by site, location, and region. Each of w

Re: [R] Mixed model Nested ANOVA

2008-02-22 Thread Mark Difford
Hi Stephen, Hopefully you will get an answer from one of the experts on mixed models who subscribe to this list. However, you should know that both lme() and lmer() currently have anova() methods. The first will give you p-values (but no SS), and the second will give you SS (but no p-values).

[R] Mixed model Nested ANOVA

2008-02-22 Thread Stephen Cole
hello R help I am trying to analyze a data set that has been collected from a hierarchical sampling design. The model should be a mixed model nested ANOVA. The purpose of my study is to analyze the variability at each spatial scale in my design (random factors, variance components), and say some