Thank you very much Thierry.

Swiftness is time in minutes.  Is it possible to handle this response
variable in a better way?

Best,

Manuel

2011/3/21 ONKELINX, Thierry <Thierry.ONKELINX@inbo.be>

> Dear Manuel,
>
> The points on a line are due to zero's in your dataset. The distance
> between this line and the other residuals depends on the number that you add
> to the respons prior to taking the log. Increasing it will make the
> difference smaller.
>
> A log transformation with zero's is something that I would try to avoid.
> Maybe a sqrt() trasnformation will do. Or glmm is the respons can be
> interpreted as some kind of counts. Another option would be to use a hurdle
> model to find the zero's and the non-zero's seperatly.
>
> Do you have an idea why the Swiftness is either zero or a quite larger
> number?
>
> Best regards,
>
> Thierry
>
>
> ----------------------------------------------------------------------------
> 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@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-sig-mixed-models-bounces@r-project.org
> > [mailto:r-sig-mixed-models-bounces@r-project.org] Namens
> > Manuel Spínola
> > Verzonden: maandag 21 maart 2011 14:15
> > Aan: r-sig-mixed-models@r-project.org
> > Onderwerp: [R-sig-ME] Residuals plot for a linear mixed model
> >
> > Dear list members,
> >
> > I got the attached residuals plot for linear mixed model
> > after logtransformationn of the response variable.
> > Is the plot telling me that I have a problem with the model
> > fitted?  If logtransformation didn't help, what are thealternatives?
> >
> >  > mode = lmer(log(Swiftness.1 + 0.05) ~ Lure + Sex +
> > Facility.Size + (1|Subject), REML = F, data = otter)  >
> > summary(mode) Linear mixed model fit by maximum likelihood
> > Formula: log(Swiftness.1 + 0.05) ~ Lure + Sex + Facility.Size + (1 |
> > Subject)
> >     Data: otter
> >   AIC   BIC logLik deviance REMLdev
> >   546 574.9   -262      524   511.5
> > Random effects:
> >   Groups   Name        Variance Std.Dev.
> >   Subject  (Intercept) 0.75907  0.87125
> >   Residual             9.33305  3.05500
> > Number of obs: 102, groups: Subject, 17
> >
> > Fixed effects:
> >                     Estimate Std. Error t value
> > (Intercept)          1.1968     1.0832   1.105
> > Lure[T.2]           -0.4375     1.0479  -0.418
> > Lure[T.3]            0.9928     1.0479   0.947
> > Lure[T.4]            0.4381     1.0479   0.418
> > Lure[T.5]           -0.3059     1.0479  -0.292
> > Lure[T.6]           -1.1340     1.0479  -1.082
> > Sex[T.1]            -0.2301     0.7411  -0.311
> > Facility.Size[T.2]   1.9357     0.9550   2.027
> > Facility.Size[T.3]   1.2889     0.9820   1.312
> >
> > Correlation of Fixed Effects:
> >              (Intr) L[T.2] L[T.3] L[T.4] L[T.5] L[T.6] S[T.1] F.S[T.2
> > Lure[T.2]   -0.484
> > Lure[T.3]   -0.484  0.500
> > Lure[T.4]   -0.484  0.500  0.500
> > Lure[T.5]   -0.484  0.500  0.500  0.500
> > Lure[T.6]   -0.484  0.500  0.500  0.500  0.500
> > Sex[T.1]    -0.342  0.000  0.000  0.000  0.000  0.000
> > Fclt.S[T.2] -0.540  0.000  0.000  0.000  0.000  0.000 -0.055
> > Fclt.S[T.3] -0.544  0.000  0.000  0.000  0.000  0.000  0.000  0.617
> >
> > predicted<-fitted(mode)
> > raw.residuals<-residuals(mode)
> > plot(predicted,raw.residuals)
> > abline(h=c(-1.96*sd(raw.residuals),0,1.96*sd(raw.residuals)))
> >
> >
> > Best,
> >
> > Manuel
> >
> >
> >
> > --
> > *Manuel Spínola, Ph.D.*
> > Instituto Internacional en Conservación y Manejo de Vida
> > Silvestre Universidad Nacional Apartado 1350-3000 Heredia
> > COSTA RICA mspinola@una.ac.cr mspinola10@gmail.com
> > Teléfono: (506) 2277-3598
> > Fax: (506) 2237-7036
> > Personal website: Lobito de río
> > <https://sites.google.com/site/lobitoderio/>
> > Institutional website: ICOMVIS <http://www.icomvis.una.ac.cr/>
> >




-- 
*Manuel Spínola, Ph.D.*
Instituto Internacional en Conservación y Manejo de Vida Silvestre
Universidad Nacional
Apartado 1350-3000
Heredia
COSTA RICA
mspinola@una.ac.cr
mspinola10@gmail.com
Teléfono: (506) 2277-3598
Fax: (506) 2237-7036
Personal website: Lobito de río <https://sites.google.com/site/lobitoderio/>
Institutional website: ICOMVIS <http://www.icomvis.una.ac.cr/>

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