[R-sig-ME] interaction terms interpretation
Joaquín Aldabe
joaquin.aldabe at gmail.com
Mon Aug 10 21:44:59 CEST 2015
Thierry, Ken and Ben, I'm following your useful recommendations. Just in
case, I'm attaching the model output in a correct format so that you can
see it.
Best,
Joaquín
2015-08-10 11:58 GMT-03:00 Joaquín Aldabe <joaquin.aldabe at gmail.com>:
> Thankyou Ben! It looks great. Cheers
> El 10/08/2015 11:54, "Ben Bolker" <bbolker at gmail.com> escribió:
>
>> Consider taking a look at
>> http://ms.mcmaster.ca/~bolker/R/misc/foxchapter/bolker_chap.html .
>>
>> On Mon, Aug 10, 2015 at 10:30 AM, Joaquín Aldabe
>> <joaquin.aldabe at gmail.com> wrote:
>> > 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]]
>> >>>
>> >>> _______________________________________________
>> >>> R-sig-mixed-models at r-project.org mailing list
>> >>> https://stat.ethz.ch/mailman/listinfo/r-sig-mixed-models
>> >>>
>> >>
>> >>
>> >>
>> >> --
>> >>
>> >> *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/
>> >>
>> >> CRICOS Provider No 00002J
>> >> This message is intended for the addressee named and m...{{dropped:12}}
>> >
>> > _______________________________________________
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>> > https://stat.ethz.ch/mailman/listinfo/r-sig-mixed-models
>>
>
--
*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>
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