[R] Mixed models fixed effects

[ONKELINX, Thierry]

Dear Emma,

Have you tried a simpler model? False convergence can be due to an
overcomplex model. Can you give a brief outline of your data? E.g. how
many sites, how many data per site, ... Cross tabulations of all pairs
of factor variables are usefull too.

HTH,

Thierry 


------------------------------------------------------------------------
----
ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek / Research Institute for Nature
and Forest
Cel biometrie, methodologie en kwaliteitszorg / Section biometrics,
methodology and 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: Emma Stone [mailto:Emma.Stone at bristol.ac.uk] 
Verzonden: vrijdag 13 maart 2009 10:50
Aan: ONKELINX, Thierry; Emma Stone; r-help at r-project.org
Onderwerp: RE: [R] Mixed models fixed effects

Hi Thierry,

That's great thanks!

I have done as you have said but I keep getting a warning message here
is 
my code:

G1Hvol<-glmer(passes~hvolume+style+habitat(1|Site),family = poisson)

And this is the message i get:
Warning message:
In mer_finalize(ans) : false convergence (8)

any ideas??

Emma


--On 11 March 2009 15:45 +0100 "ONKELINX, Thierry" 
<Thierry.ONKELINX at inbo.be> wrote:

> Hi Emma,
>
> Continuous predictors are no problem at all. You can mix both
continuous
> and categorial predictors if needed. I suppose your response are
counts
> (the number of bats that passes)? In that case a generalised linear
> mixed model is more appropriate. With the lme4 package you could try
> something like this:
>
> library(lme4)
> Model <- glmer(BatPasses ~ Width + Height + (1|Site), family =
poisson)
>
> HTH,
>
> Thierry
>
> PS There is a mailing list dedicated to mixed models:
R-Sig-MixedModels
>
------------------------------------------------------------------------
> ----
> ir. Thierry Onkelinx
> Instituut voor natuur- en bosonderzoek / Research Institute for Nature
> and Forest
> Cel biometrie, methodologie en kwaliteitszorg / Section biometrics,
> methodology and 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 Emma Stone
> Verzonden: woensdag 11 maart 2009 15:29
> Aan: r-help at r-project.org
> Onderwerp: Re: [R] Mixed models fixed effects
>
> Dear All,
>
> This may sound like a dumb question but I am trying to use a mixed
model
> to
> determine the predictors of bat activity along hedges within 8 sites.
So
> my
> response is continuous (bat passes) my predictors fixed effects are
> continuous (height metres), width (metres) etc and the random effect
is
> site  - can you tell me if the fixed effects can be continuous as all
> the
> examples I have read show them as categorical, but this is not covered
> in
> any documents I can find.
>
> Help!
>
> Emma
>
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----------------------
Emma Stone
Postgraduate Researcher
Bat Ecology and Bioacoustics Lab
& Mammal Research Unit
School of Biological Sciences,
University of Bristol, Woodland Road,
Bristol, BS8 1UG
Email: emma.stone at bristol.ac.uk



Dit bericht en eventuele bijlagen geven enkel de visie van de schrijver weer 
en binden het INBO onder geen enkel beding, zolang dit bericht niet bevestigd is
door een geldig ondertekend document. The views expressed in  this message 
and any annex are purely those of the writer and may not be regarded as stating 
an official position of INBO, as long as the message is not confirmed by a duly 
signed document.