[R-sig-ME] zero-inflation beta or gamma model?
bbo|ker @end|ng |rom gm@||@com
Thu Jan 9 15:26:36 CET 2020
The zero-inflation stuff is only available in the development
version of glmmTMB at the moment ... although we hope to submit a new
version to CRAN in the very near future. (See
instructions on installing the development version.)
On Thu, Jan 9, 2020 at 5:28 AM Luca Santini <luca.santini.eco using gmail.com> wrote:
> I have a response variable expressed as proportion that varies from 0 to 1. The variable is highly left skewed, and about half of the values are zeros. I found a previous question related to a possible use of beta family together with a zero-inflation, to which B. Bolker replied it was possible using a hurdle approach in the glmmTMB package. I rescaled the response to 0 - 0.999 (only 1 value is = 1) and tried this approach.
> However, when I run
> mod<-glmmTMB(TerrBeta2 ~ 1 + (1|Family/Genus/Species) + (1|Site/Year/Month), family=beta_family(), ziformula=~., data=data2)
> I get the following error message (looks like the ziformula argument is ignored)
> Error in eval(family$initialize) : y values must be 0 < y < 1
> I also tried to specify the family differently
> mod<-glmmTMB(TerrBeta2 ~ 1 + (1|Family/Genus/Species) + (1|Site/Year/Month), family=list(family="beta",link="logit"), ziformula=~., data=data2)
> But I get this
> Error in nlminb(start = par, objective = fn, gradient = gr, control = control$optCtrl) :
> gradient function must return a numeric vector of length 15
> In addition: Warning messages:
> 1: In glmmTMB(TerrBeta2 ~ 1 + (1 | Family/Genus/Species) + (1 | Site/Year/Month), :
> some components missing from ‘family’: downstream methods may fail
> 2: In mkTMBStruc(formula, ziformula, dispformula, combForm, mf, fr, :
> specifying ‘family’ as a plain list is deprecated
> 3: In nlminb(start = par, objective = fn, gradient = gr, control = control$optCtrl) :
> NA/NaN function evaluation
> Timing stopped at: 0.626 0.065 0.689
> Any suggestion?
> Another option to avoid rescaling the variable may be using the gamma family, but I get into the same error messages.
> Any suggestion would be greatly appreciated!
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