[R-sig-ME] glm question

[Joaquín Aldabe]

Thanks Thierry, I´ve attached the data in excel format and the script in
txt. I´ll also write to r-help.
Best wishes,
Joaquín.

2015-08-19 11:54 GMT-03:00 Thierry Onkelinx <thierry.onkelinx at inbo.be>:

> Dear Joaquin,
>
> Your attachments got stripped. It's better to put them somewhere on
> line an add a link in your message.
>
> If your problem concerns a glm() then r-help would be a better mailing
> list. If it is about glmer() then this mailing list is fine.
>
> 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
>
>
> 2015-08-19 16:39 GMT+02:00 Joaquín Aldabe <joaquin.aldabe at gmail.com>:
> > Dear All, I´m running a glm with poisson errors and have a doubt when
> > ploting the predicted values. One of my variables has a positive slope in
> > the summary output, but when I plot the predicted values on the original
> > plot it draws a line with negative slope. I appreciate your comments on
> > this and any other aspect of the analysis.
> >
> > Attached is the script and data.
> >
> > Thanks in advanced,
> >
> > Joaquín.
> >
> > pd. If this is not the correct forum to ask about glm, please let me
> know.
> >
> > --
> > *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>
> > _______________________________________________
> > R-sig-mixed-models at r-project.org mailing list
> > 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>
-------------- next part --------------
my4<-read.table(file.choose(), header=T, dec=",")
my4s<-as.data.frame(scale(my4[,c(6,10,12,13,16)], center=T, scale=T))
my4S<-cbind(BBSA=my4$BBSA, Field_name=my4$Field_name,Grassland_type=my4$Grassland_type, Flood=my4$Flood, Year=my4$Year,my4s)

m2.glm=glm(BBSA~AMGP+Distance_to_lagoon+Grass_height, family="quasipoisson", data=my4S
summary(m2.glm)
#residuales
par(mfrow=c(2,2))
plot(m2.glm)#pretty good

#predict
amgp=seq(-0.51, 5.44, length.out=100)
grass=seq(-0.85,2.83, length.out=100)
dist=seq(-1.59,1.53, length.out=100)
newdata=data.frame(AMGP=amgp, Distance_to_lagoon=dist,Grass_height=grass)
pred.m2.glm=exp(predict(m2.glm,newdata))
plot(BBSA~Grass_height, data=my4S)
lines(newdata$Grass_height,pred.m2.glm)
plot(BBSA~AMGP, data=my4S)
lines(newdata$AMGP,pred.m2.glm)#why negative slope if summary output is positive
plot(BBSA~Distance_to_lagoon, data=my4S)
lines(newdata$Distance_to_lagoon, pred.m2.glm)