Re: [R-sig-eco] Possible bug with dredge function

2011-12-14 Thread Dunbar, Michael J.
but be careful how much you interpret this. Regards Mike From: Fernando Schmidt [mailto:schmidt...@gmail.com] Sent: 14 December 2011 11:40 To: Dunbar, Michael J. Cc: r-sig-ecology@r-project.org Subject: Re: [R-sig-eco] Possible bug with dredge function Dear Mike, Thanks for your help. To answer

Re: [R-sig-eco] gam variable selection

2011-09-28 Thread Dunbar, Michael J.
Hi Bex Did you mean the dredge function from the MuMIn package? I'm not really sure what you mean by it does not take into account correlates or significance. The point about dredge is that it is part of a family of functions for multi-model inference which specifically avoid concepts of

Re: [R-sig-eco] Appropriate mixed model?

2011-09-16 Thread Dunbar, Michael J.
Hi Rob As it stands your model won't really do what you are expecting. Start with a model like this: fish.mod1-lmer(fishsize ~ pH + landuse + conductivity + (1 | subcatchment), data=mydata) You don't say whether you have multiple samples within each subcatchment + year combination, or

Re: [R-sig-eco] plot confidence intervals of a line from a mixed model

2011-09-07 Thread Dunbar, Michael J.
Hi Rob A couple of suggestions 1. You can use the glht command in the multcomp to get predictions for different factor levels with simultaneous se's / ci's, you just need to formulate the correct contrast(s) 2. You can make ad-hoc predictions by matrix-multiplying the parameter estimates

Re: [R-sig-eco] logistic regression and spatial autocorrelation

2011-08-25 Thread Dunbar, Michael J.
Hi Tim You haven't really explained where your group variable in the glmm has come from. Moving from glm to glmm you've changed two things, adding the grouping and the autocorrelation as well. You have to be very careful when using the autocorrelation function. As it stands the model will

Re: [R-sig-eco] logistic regression and spatial autocorrelation

2011-08-25 Thread Dunbar, Michael J.
, then the valley splits to form two secondary tributaries 'vord' and 'hint'. Given that my points become less well order toward high elevation should I use form= ~1|group? On 25.08.11 11:21, Dunbar, Michael J. wrote: Hi Tim You haven't really explained where your group variable in the glmm has

Re: [R-sig-eco] random effects in a linear mixed model

2011-08-22 Thread Dunbar, Michael J.
Edgar I agree with what Chris says (1 + BOAT | fYEAR) makes no sense It is probably (1|BOAT) + (1|fYEAR) that you want Providing you have enough boats and years to estimate variance components for these two factors: please feel free to post any further queries but you will need to provide

Re: [R-sig-eco] Partially non-independent ANOVA?

2011-06-23 Thread Dunbar, Michael J.
Dear Cliff Using a mixed-effects model (also variously termed multilevel or hierarchical model) could well be what you are looking for. These are implemented in several R packages. In your study, in mixed model parlance, patient identifier would be a random effect (you don't say how many

Re: [R-sig-eco] CALIBRATE program

2011-03-14 Thread Dunbar, Michael J.
Have a look at the bio.infer package Regards Mike -Original Message- From: r-sig-ecology-boun...@r-project.org [mailto:r-sig-ecology-boun...@r-project.org] On Behalf Of Yong Zhang Sent: 14 March 2011 09:10 To: r-sig-ecology Subject: [R-sig-eco] CALIBRATE program Hi all, Today, I

Re: [R-sig-eco] nested factor for which i would like a parameter estimate

2011-03-13 Thread Dunbar, Michael J.
Hi Doug Your first model can't be right, as AM/PM is clearly a fixed effect: it has just two levels and you are only interested in making inferences about those two levels. So you can't have AMPM on the right of the random part of the model. Try not to think of nesting fixed effects in random

Re: [R-sig-eco] What statistical analysis should I take??

2011-01-12 Thread Dunbar, Michael J.
Dear Yong The simplest approach would be to calculate a phi value for each stream, and then apply conventional anova. There is some background on phi here: http://en.wikipedia.org/wiki/Particle_size_%28grain_size%29 There is an example of a simple algorithm to calculate phi from discrete

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

2010-12-08 Thread Dunbar, Michael J.
, is handled automatically. If you don't believe me then you may wish to ask on the r sig for mixed models. Regards Mike -Original Message- From: Hedberg Peter [mailto:phedb...@biol.uw.edu.pl] Sent: 07 December 2010 19:00 To: Dunbar, Michael J.; r-sig-ecology@r-project.org Subject: Sv: RE: [R