[R-sig-ME] interaction terms interpretation

[Joaquín Aldabe]

Thankyoy very much Ken and Thierry. I'll try that. Is there any specific
function for making graphs of the model? I appreciate recommendations or
citations to explore how to graph model results. Thanks again. Joaquin
El 10/08/2015 07:36, "Ken Beath" <ken.beath at mq.edu.au> escribió:

> There is actually a continuous third order interaction, which are just
> about impossible to interpret.
>
> As well as the graphs, which you always should start with, think about
> what is sensible for the model. Should any of the predictors be log-scaled?
> As AMGP is a count it wouldn't be surprising it it is, or use log(1+x) if
> there are zeroes.
>
> Look at diagnostic plots and make sure that everything is fine, especially
> that there are no outliers which might be causing the interaction.
>
> Ken
>
> On 10 August 2015 at 17:02, Thierry Onkelinx <thierry.onkelinx at inbo.be>
> wrote:
>
>> Dear Joaquin,
>>
>> Your mail is mangled because you send it in HTML. This makes the model
>> output very hard to read.
>>
>> It's impossible to interpret model output without thorough knowledge of
>> the
>> dataset. I suggest that you try to make some graphs of the model.
>>
>> Best regards,
>>
>> ir. Thierry Onkelinx
>> Instituut voor natuur- en bosonderzoek / Research Institute for Nature and
>> Forest
>> team Biometrie & Kwaliteitszorg / team Biometrics & Quality Assurance
>> Kliniekstraat 25
>> 1070 Anderlecht
>> Belgium
>>
>> 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
>>
>> 2015-08-07 21:27 GMT+02:00 Joaquín Aldabe <joaquin.aldabe at gmail.com>:
>>
>> > Hi all, I´m running a mixed model with poisson error distribution as I
>> have
>> > count data of a shorebird species. My predictors are AMGP (another
>> > shorebird that is usually associated to "my" species and probably has
>> > ecological influence on it), grass height and field distance to the
>> lagoon.
>> >
>> > I´m having a hard time trying to interpret second order interactions. I
>> > appreciate your comments of references recommendations. Here is the
>> output
>> > of my model. All the best, Joaquín.
>> >
>> > Call:glmmadmb(formula = BBSA ~ AMGP * Grass_height *
>> > Distance_to_lagoon +     (1 | Field_name) + offset(log(Field_area.o)),
>> > data = my4S,     family = "nbinom1", zeroInflation = TRUE)
>> > AIC: 226
>> > Coefficients:                                     Estimate Std. Error
>> > z value Pr(>|z|)    (Intercept)                           -5.8797
>> > 1.2250   -4.80  1.6e-06 ***AMGP
>> > 3.3086     1.0246    3.23   0.0012 ** Grass_height
>> >      -4.1592     1.9961   -2.08   0.0372 *  Distance_to_lagoon
>> >            -0.5029     1.3929   -0.36   0.7180    AMGP:Grass_height
>> >                   2.9442     1.5142    1.94   0.0518 .
>> > AMGP:Distance_to_lagoon               -2.4695     0.9632   -2.56
>> > 0.0104 *  Grass_height:Distance_to_lagoon        0.0339     2.0065
>> > 0.02   0.9865    AMGP:Grass_height:Distance_to_lagoon  -4.0363
>> > 1.3264   -3.04   0.0023 ** ---Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01
>> > ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
>> > Number of observations: total=64, Field_name=16 Random effect
>> > variance(s):Group=Field_name            Variance StdDev(Intercept)
>> > 0.03721 0.1929
>> > Negative binomial dispersion parameter: 20.633 (std. err.:
>> > 7.4042)Zero-inflation: 1e-06  (std. err.:  6.8336e-09 )
>> > Log-likelihood: -102
>> >
>> >
>> > --
>> > *Joaquín Aldabe*
>> >
>> > *Grupo Biodiversidad, Ambiente y Sociedad*
>> > Centro Universitario de la Región Este, Universidad de la República
>> > Ruta 15 (y Ruta 9), Km 28.500, Departamento de Rocha
>> >
>> > *Departamento de Conservación*
>> > Aves Uruguay
>> > BirdLife International
>> > Canelones 1164, Montevideo
>> >
>> > https://sites.google.com/site/joaquin.aldabe
>> > <https://sites.google.com/site/perfilprofesionaljoaquinaldabe>
>> >
>> >         [[alternative HTML version deleted]]
>> >
>> > _______________________________________________
>> > R-sig-mixed-models at r-project.org mailing list
>> > https://stat.ethz.ch/mailman/listinfo/r-sig-mixed-models
>> >
>>
>>         [[alternative HTML version deleted]]
>>
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>>
>
>
>
> --
>
> *Ken Beath*
> Lecturer
> Statistics Department
> MACQUARIE UNIVERSITY NSW 2109, Australia
>
> Phone: +61 (0)2 9850 8516
>
> Level 2, AHH
> http://stat.mq.edu.au/our_staff/staff_-_alphabetical/staff/beath,_ken/
>
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