[R-sig-ME] Question about zero-inflated Poisson glmer

Philipp Singer killver at gmail.com
Mon Jun 27 17:46:33 CEST 2016


Well, as posted beforehand the std dev is 9.5 ... so does not seem too 
good then :/

Any other idea?

On 27.06.2016 17:31, Thierry Onkelinx wrote:
> Dear Philipp,
>
> You've been bitten by observation level random effects. I've put 
> together a document about it on http://rpubs.com/INBOstats/OLRE. 
> Bottomline you're OKish when the standard devation of the OLRE smaller 
> than 1. You're in trouble when it's above 3. In between you need to 
> check the model carefully.
>
> 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
>
> 2016-06-27 16:17 GMT+02:00 Philipp Singer <killver at gmail.com 
> <mailto:killver at gmail.com>>:
>
>     Here is the fitted vs. residual plot for the observation-level
>     poisson model where the observation level has been removed as
>     taken from:
>     https://stat.ethz.ch/pipermail/r-sig-mixed-models/2013q3/020817.html
>
>     So basically the prediction is always close to zero.
>
>     Note that this is just on a very small sample (1000 data points).
>
>     If I fit a nbinom2 to this smalle sample, I get predictions that
>     are always around ~20 (but never zero). Both plots are attached.
>
>     What I am wondering is whether I can do inference on a fixed
>     parameter in my model which is my main task of this study. The
>     effect is similar in the different models and in general I am only
>     itnerested in whether it is positive/negative and "significant"
>     which it is. However, as can be seen, the prediction looks not too
>     good here.
>
>
>
>
>     2016-06-27 15:18 GMT+02:00 Philipp Singer <killver at gmail.com
>     <mailto:killver at gmail.com>>:
>
>         The variance is:
>
>         Conditional model:
>           Groups            Name        Variance  Std.Dev.
>           obs               (Intercept) 8.991e+01 9.4823139
>
>
>
>         2016-06-27 15:06 GMT+02:00 Thierry Onkelinx
>         <thierry.onkelinx at inbo.be <mailto:thierry.onkelinx at inbo.be>>:
>
>             Dear Philipp,
>
>             How strong is the variance of the observation level random
>             effect? I would trust a model with large OLRE variance.
>
>             Best regards,
>
>             Thierry
>
>             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
>
>             2016-06-27 14:59 GMT+02:00 Philipp Singer
>             <killver at gmail.com <mailto:killver at gmail.com>>:
>
>                 I have now played around more with the data an the
>                 models both using lme4
>                 and glmmTMB.
>
>                 I can report the following:
>
>                 Modeling the data with a zero-inflated Poisson
>                 improves the model
>                 significantly. However, when calling predict and
>                 simulating rpoissons, I
>                 end up with nearly no values that are zero (in the
>                 original data there are
>                 96% zero).
>
>                 When I model the data with overdisperion by including
>                 an observation-level
>                 random effect, I can also improve the model (not
>                 surprisingly due to the
>                 random effect). When I predict outcomes by ignoring
>                 the observation-level
>                 random effect (in lme4), I receive bad prediction if I
>                 compare it to the
>                 original data. While many zeros can be captured (of
>                 course), the positive
>                 outcomes can not be captured well.
>
>                 Combining zero inflation and overdispersion further
>                 improves the model, but
>                 I can only do that with glmmTMB and then have troubles
>                 doing predictions
>                 ignoring the observation-level random effect.
>
>                 Another side question:
>
>                 In lme4, when I do:
>
>                 m = glm(x~1,family="poisson")
>                 rpois(n=len(data),lambda=predict(m,
>                 type='response',re.form=NA)
>
>                 vs.
>
>                 simulate(1,m,re.form=NA)
>
>                 I receive different outcomes? Do I understand these
>                 function wrongly?
>
>                 Would appreciate some more help/pointers!
>
>                 Thanks,
>                 Philipp
>
>                 2016-06-24 15:52 GMT+02:00 Philipp Singer
>                 <killver at gmail.com <mailto:killver at gmail.com>>:
>
>                 > Thanks - I started an issue there to answer some of
>                 my questions.
>                 >
>                 > Regarding the installation: I was trying to somehow
>                 do it in anaconda with
>                 > a specific R kernel and had some issues. I am trying
>                 to resort that with
>                 > the anaconda guys though, if I have a tutorial on
>                 how to properly setup
>                 > glmmTMB in anaconda, I will let you know. The
>                 install worked fine in my
>                 > standard R environment.
>                 >
>                 >
>                 > On 24.06.2016 15 <tel:24.06.2016%2015>:40, Ben
>                 Bolker wrote:
>                 >
>                 >>   Probably for now the glmmTMB issues page is best.
>                 >>
>                 >>   When you go there:
>                 >>
>                 >>    - details on installation problems/hiccups would
>                 be useful
>                 >>    - a reproducible example for the problem listed
>                 below would be useful
>                 >>    - dispformula is for allowing
>                 dispersion/residual variance to vary
>                 >> with covariates (i.e., modeling heteroscedasticity)
>                 >>
>                 >>    cheers
>                 >>      Ben Bolker
>                 >>
>                 >>
>                 >> On 16-06-24 09:13 AM, Philipp Singer wrote:
>                 >>
>                 >>> Update, I tried it like that, but receive an error
>                 message.
>                 >>>
>                 >>> Warning message:
>                 >>> In nlminb(start = par, objective = fn, gradient =
>                 gr): NA/NaN function
>                 >>> evaluation
>                 >>>
>                 >>> Error in solve.default(hessian.fixed): Lapack
>                 routine dgesv: system is
>                 >>> exactly singular: U[3,3] = 0
>                 >>> Traceback:
>                 >>>
>                 >>> 1. glmmTMB(y ~ 1 + x + (1 | b),
>                 >>>    .  data = data, family = "poisson", dispformula
>                 = ~1 + x)
>                 >>> 2. sdreport(obj)
>                 >>> 3. solve(hessian.fixed)
>                 >>> 4. solve(hessian.fixed)
>                 >>> 5. solve.default(hessian.fixed)
>                 >>>
>                 >>> Any ideas on that?
>                 >>>
>                 >>> BTW: Is it fine to post glmmTMB questions here, or
>                 should I rather use
>                 >>> the github issue page, or is there maybe a
>                 dedicated mailing list?
>                 >>>
>                 >>> Thanks,
>                 >>> Philipp
>                 >>>
>                 >>> On 24.06.2016 14:35, Philipp Singer wrote:
>                 >>>
>                 >>>> It indeed seems to run quite fast; had some
>                 trouble installing, but
>                 >>>> works now on my 3.3 R setup.
>                 >>>>
>                 >>>> One question I have is regarding the
>                 specification of dispersion as I
>                 >>>> need to specify the dispformula. What is the
>                 difference here between
>                 >>>> just specifying fixed effects vs. also the random
>                 effects?
>                 >>>>
>                 >>>> On 23.06.2016 23:07, Mollie Brooks wrote:
>                 >>>>
>                 >>>>> glmmTMB does crossed RE. Ben did some timings in
>                 vignette("glmmTMB")
>                 >>>>> and it was 2.3 times faster than glmer for one
>                 simple GLMM.
>                 >>>>>
>                 >>>>>
>                 >>>>> On 23Jun 2016, at 10:44, Philipp Singer
>                 <killver at gmail.com <mailto:killver at gmail.com>> wrote:
>                 >>>>>>
>                 >>>>>> Did try glmmADMB but unfortunately it is way
>                 too slow for my data.
>                 >>>>>>
>                 >>>>>> Did not know about glmmTMB, will try it out.
>                 Does it work with
>                 >>>>>> crossed random effects and how does it scale
>                 with more data? I will
>                 >>>>>> check the docu and try it though. Thanks for
>                 the info.
>                 >>>>>>
>                 >>>>>> On 23.06.2016 19:14, Ben Bolker wrote:
>                 >>>>>>
>                 >>>>>>>   I would also comment that glmmTMB is likely
>                 to be much faster
>                 >>>>>>> than the
>                 >>>>>>> lme4-based EM approach ...
>                 >>>>>>>
>                 >>>>>>>   cheers
>                 >>>>>>>     Ben B.
>                 >>>>>>>
>                 >>>>>>> On 16-06-23 12:47 PM, Mollie Brooks wrote:
>                 >>>>>>>
>                 >>>>>>>> Hi Philipp,
>                 >>>>>>>>
>                 >>>>>>>> You could also try fitting the model with and
>                 without ZI using
>                 >>>>>>>> either
>                 >>>>>>>> glmmADMB or glmmTMB. Then compare the AICs. I
>                 believe model
>                 >>>>>>>> selection
>                 >>>>>>>> is useful for this, but I could be missing
>                 something since the
>                 >>>>>>>> simulation procedure that Thierry described
>                 seems to recommended
>                 >>>>>>>> more
>                 >>>>>>>> often.
>                 >>>>>>>>
>                 >>>>>>>> https://github.com/glmmTMB/glmmTMB
>                 >>>>>>>> http://glmmadmb.r-forge.r-project.org
>                 >>>>>>>>
>                 >>>>>>>> glmmTMB is still in the development phase,
>                 but we’ve done a lot of
>                 >>>>>>>> testing.
>                 >>>>>>>>
>                 >>>>>>>> cheers, Mollie
>                 >>>>>>>>
>                 >>>>>>>> ------------------------ Mollie Brooks, PhD
>                 Postdoctoral Researcher,
>                 >>>>>>>> Population Ecology Research Group Department
>                 of Evolutionary Biology
>                 >>>>>>>> & Environmental Studies, University of Zürich
>                 >>>>>>>> http://www.popecol.org/team/mollie-brooks/
>                 >>>>>>>>
>                 >>>>>>>>
>                 >>>>>>>> On 23Jun 2016, at 8:22, Philipp Singer
>                 <killver at gmail.com <mailto:killver at gmail.com>> wrote:
>                 >>>>>>>>>
>                 >>>>>>>>> Thanks, great information, that is really
>                 helpful.
>                 >>>>>>>>>
>                 >>>>>>>>> I agree that those are different things,
>                 however when using a
>                 >>>>>>>>> random effect for overdispersion, I can
>                 simulate the same number of
>                 >>>>>>>>> zero outcomes (~95%).
>                 >>>>>>>>>
>                 >>>>>>>>> On 23.06.2016 15:50, Thierry Onkelinx wrote:
>                 >>>>>>>>>
>                 >>>>>>>>>> Be careful when using overdispersion to
>                 model zero-inflation.
>                 >>>>>>>>>> Those are two different things.
>                 >>>>>>>>>>
>                 >>>>>>>>>> I've put some information together in
>                 >>>>>>>>>> http://rpubs.com/INBOstats/zeroinflation
>                 >>>>>>>>>>
>                 >>>>>>>>>> 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
>                 >>>>>>>>>>
>                 >>>>>>>>>> 2016-06-23 12:42 GMT+02:00 Philipp Singer
>                 <killver at gmail.com <mailto:killver at gmail.com>
>                 >>>>>>>>>> <mailto:killver at gmail.com
>                 <mailto:killver at gmail.com> <mailto:killver at gmail.com
>                 <mailto:killver at gmail.com>>>>:
>                 >>>>>>>>>>
>                 >>>>>>>>>> Thanks! Actually, accounting for
>                 overdispersion is super
>                 >>>>>>>>>> important as it seems, then the zeros can
>                 be captured well.
>                 >>>>>>>>>>
>                 >>>>>>>>>>
>                 >>>>>>>>>> On 23.06.2016 11:50, Thierry Onkelinx wrote:
>                 >>>>>>>>>>
>                 >>>>>>>>>>> Dear Philipp,
>                 >>>>>>>>>>>
>                 >>>>>>>>>>> 1. Fit a Poisson model to the data. 2.
>                 Simulate a new response
>                 >>>>>>>>>>> vector for the dataset according to the
>                 model. 3. Count the
>                 >>>>>>>>>>> number of zero's in the simulated response
>                 vector. 4. Repeat
>                 >>>>>>>>>>> step 2 and 3 a decent number of time and
>                 plot a histogram of
>                 >>>>>>>>>>> the number of zero's in the simulation. If
>                 the number of zero's
>                 >>>>>>>>>>> in the original dataset is larger than
>                 those in the
>                 >>>>>>>>>>> simulations, then the model can't capture
>                 all zero's. In such
>                 >>>>>>>>>>> case, first try to update the model and
>                 repeat the procedure.
>                 >>>>>>>>>>> If that fails, look for zero-inflated models.
>                 >>>>>>>>>>>
>                 >>>>>>>>>>> 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
>                 >>>>>>>>>>>
>                 >>>>>>>>>>> 2016-06-23 11:27 GMT+02:00 Philipp Singer
>                 <killver at gmail.com <mailto:killver at gmail.com>
>                 >>>>>>>>>>> <mailto:killver at gmail.com
>                 <mailto:killver at gmail.com> <mailto:killver at gmail.com
>                 <mailto:killver at gmail.com>>>>:
>                 >>>>>>>>>>>
>                 >>>>>>>>>>> Thanks Thierry - That totally makes sense.
>                 Is there some way of
>                 >>>>>>>>>>> formally checking that, except thinking
>                 about the setting and
>                 >>>>>>>>>>> underlying processes?
>                 >>>>>>>>>>>
>                 >>>>>>>>>>> On 23.06.2016 11:04, Thierry Onkelinx wrote:
>                 >>>>>>>>>>>
>                 >>>>>>>>>>>> Dear Philipp,
>                 >>>>>>>>>>>>
>                 >>>>>>>>>>>> Do you have just lots of zero's, or more
>                 zero's than the
>                 >>>>>>>>>>>>
>                 >>>>>>>>>>> Poisson
>                 >>>>>>>>>>>
>                 >>>>>>>>>>>> distribution can explain? Those are two
>                 different things.
>                 >>>>>>>>>>>>
>                 >>>>>>>>>>> The example
>                 >>>>>>>>>>>
>                 >>>>>>>>>>>> below generates data from a Poisson
>                 distribution and has
>                 >>>>>>>>>>>>
>                 >>>>>>>>>>> 99% zero's
>                 >>>>>>>>>>>
>                 >>>>>>>>>>>> but no zero-inflation. The second example
>                 has only 1%
>                 >>>>>>>>>>>>
>                 >>>>>>>>>>> zero's but is
>                 >>>>>>>>>>>
>                 >>>>>>>>>>>> clearly zero-inflated.
>                 >>>>>>>>>>>>
>                 >>>>>>>>>>>> set.seed(1) n <- 1e8 sim <- rpois(n,
>                 lambda = 0.01) mean(sim
>                 >>>>>>>>>>>> == 0) hist(sim)
>                 >>>>>>>>>>>>
>                 >>>>>>>>>>>> sim.infl <- rbinom(n, size = 1, prob =
>                 0.99) * rpois(n,
>                 >>>>>>>>>>>>
>                 >>>>>>>>>>> lambda = 1000)
>                 >>>>>>>>>>>
>                 >>>>>>>>>>>> mean(sim.infl == 0) hist(sim.infl)
>                 >>>>>>>>>>>>
>                 >>>>>>>>>>>> So before looking for zero-inflated
>                 models, try to model
>                 >>>>>>>>>>>>
>                 >>>>>>>>>>> the zero's.
>                 >>>>>>>>>>>
>                 >>>>>>>>>>>> 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
>                 >>>>>>>>>>>>
>                 >>>>>>>>>>>> 2016-06-23 10:07 GMT+02:00 Philipp Singer
>                 >>>>>>>>>>>>
>                 >>>>>>>>>>> <killver at gmail.com
>                 <mailto:killver at gmail.com> <mailto:killver at gmail.com
>                 <mailto:killver at gmail.com>>
>                 >>>>>>>>>>> <mailto:killver at gmail.com
>                 <mailto:killver at gmail.com> <mailto:killver at gmail.com
>                 <mailto:killver at gmail.com>>>
>                 >>>>>>>>>>>
>                 >>>>>>>>>>>> <mailto:killver at gmail.com
>                 <mailto:killver at gmail.com> <mailto:killver at gmail.com
>                 <mailto:killver at gmail.com>>
>                 >>>>>>>>>>>> <mailto:killver at gmail.com
>                 <mailto:killver at gmail.com> <mailto:killver at gmail.com
>                 <mailto:killver at gmail.com>>>>>:
>                 >>>>>>>>>>>>
>                 >>>>>>>>>>>> Dear group - I am currently fitting a
>                 Poisson glmer
>                 >>>>>>>>>>>>
>                 >>>>>>>>>>> where I have
>                 >>>>>>>>>>>
>                 >>>>>>>>>>>> an excess of outcomes that are zero
>                 (>95%). I am now
>                 >>>>>>>>>>>>
>                 >>>>>>>>>>> debating on
>                 >>>>>>>>>>>
>                 >>>>>>>>>>>> how to proceed and came up with three
>                 options:
>                 >>>>>>>>>>>>
>                 >>>>>>>>>>>> 1.) Just fit a regular glmer to the
>                 complete data. I am
>                 >>>>>>>>>>>>
>                 >>>>>>>>>>> not fully
>                 >>>>>>>>>>>
>                 >>>>>>>>>>>> sure how interpret the coefficients then,
>                 are they more
>                 >>>>>>>>>>>>
>                 >>>>>>>>>>> optimizing
>                 >>>>>>>>>>>
>                 >>>>>>>>>>>> towards distinguishing zero and non-zero,
>                 or also
>                 >>>>>>>>>>>>
>                 >>>>>>>>>>> capturing the
>                 >>>>>>>>>>>
>                 >>>>>>>>>>>> differences in those outcomes that are
>                 non-zero?
>                 >>>>>>>>>>>>
>                 >>>>>>>>>>>> 2.) Leave all zeros out of the data and
>                 fit a glmer to
>                 >>>>>>>>>>>>
>                 >>>>>>>>>>> only those
>                 >>>>>>>>>>>
>                 >>>>>>>>>>>> outcomes that are non-zero. Then, I would
>                 only learn about
>                 >>>>>>>>>>>> differences in the non-zero outcomes though.
>                 >>>>>>>>>>>>
>                 >>>>>>>>>>>> 3.) Use a zero-inflated Poisson model. My
>                 data is quite
>                 >>>>>>>>>>>> large-scale, so I am currently playing
>                 around with the EM
>                 >>>>>>>>>>>> implementation of Bolker et al. that
>                 alternates between
>                 >>>>>>>>>>>>
>                 >>>>>>>>>>> fitting a
>                 >>>>>>>>>>>
>                 >>>>>>>>>>>> glmer with data that are weighted
>                 according to their zero
>                 >>>>>>>>>>>> probability, and fitting a logistic
>                 regression for the
>                 >>>>>>>>>>>>
>                 >>>>>>>>>>> probability
>                 >>>>>>>>>>>
>                 >>>>>>>>>>>> that a data point is zero. The method is
>                 elaborated for
>                 >>>>>>>>>>>>
>                 >>>>>>>>>>> the OWL
>                 >>>>>>>>>>>
>                 >>>>>>>>>>>> data in:
>                 >>>>>>>>>>>>
>                 >>>>>>>>>>>>
>                 >>>>>>>>>>>
>                 https://groups.nceas.ucsb.edu/non-linear-modeling/projects/owls/WRITEUP/owls.pdf
>                 >>>>>>>>>>> <
>                 >>>>>>>>>>>
>                 https://groups.nceas.ucsb.edu/non-linear-modeling/projects/owls/WRITEUP/owls.pdf
>                 >>>>>>>>>>> >
>                 >>>>>>>>>>>
>                 >>>>>>>>>> I am not fully sure how to interpret the
>                 results for the
>                 >>>>>>>
>                 >>>>>>>> zero-inflated version though. Would I need to
>                 interpret the
>                 >>>>>>>>>>>> coefficients for the result of the glmer
>                 similar to as
>                 >>>>>>>>>>>>
>                 >>>>>>>>>>> I would do
>                 >>>>>>>>>>>
>                 >>>>>>>>>>>> for my idea of 2)? And then on top of
>                 that interpret the
>                 >>>>>>>>>>>> coefficients for the logistic regression
>                 regarding whether
>                 >>>>>>>>>>>> something is in the perfect or imperfect
>                 state? I am
>                 >>>>>>>>>>>>
>                 >>>>>>>>>>> also not
>                 >>>>>>>>>>>
>                 >>>>>>>>>>>> quite sure what the common approach for
>                 the zformula is
>                 >>>>>>>>>>>>
>                 >>>>>>>>>>> here. The
>                 >>>>>>>>>>>
>                 >>>>>>>>>>>> OWL elaborations only use zformula=z~1,
>                 so no random
>                 >>>>>>>>>>>>
>                 >>>>>>>>>>> effect; I
>                 >>>>>>>>>>>
>                 >>>>>>>>>>>> would use the same formula as for the glmer.
>                 >>>>>>>>>>>>
>                 >>>>>>>>>>>> I am appreciating some help and pointers.
>                 >>>>>>>>>>>>
>                 >>>>>>>>>>>> Thanks! Philipp
>                 >>>>>>>>>>>>
>                 >>>>>>>>>>>>
>                 _______________________________________________
>                 >>>>>>>>>>>> R-sig-mixed-models at r-project.org
>                 <mailto:R-sig-mixed-models at r-project.org>
>                 >>>>>>>>>>>> <mailto:R-sig-mixed-models at r-project.org
>                 <mailto:R-sig-mixed-models at r-project.org>>
>                 >>>>>>>>>>>> <mailto:R-sig-mixed-models at r-project.org
>                 <mailto:R-sig-mixed-models at r-project.org>>
>                 >>>>>>>>>>>>
>                 >>>>>>>>>>> <mailto:R-sig-mixed-models at r-project.org
>                 <mailto:R-sig-mixed-models at r-project.org>
>                 >>>>>>>>>>> <mailto:R-sig-mixed-models at r-project.org
>                 <mailto:R-sig-mixed-models at r-project.org>>>
>                 >>>>>>>>>>>
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>                 >>>>>>>>>>>> <mailto:R-sig-mixed-models at r-project.org
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>                 >>>>>>>>>>>>
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