Following DHARMa diagnostic tests revealing zero-inflation
(ratioObsSim = 32.663, p < 2.2e-16) and over-dispersion
(ratioObsSim = 1.5757, p = 0.104)
I am attempting to run a zero-inflated negative binomial model using the
glmmTMB function of the
glmmTMB package in R. My model code is in the following format:
model<-glmmTMB(Y~X1 * X2 + (1|R1) + (1|R2), family = "nbinom1", ziformula = ~X1 * X2 + (1|R1) + (1|R2), data = dataset).
X1 and X2 are my fixed effects (one continuous and one categorical) and R1 and R2 are my two fully crossed random effects (one continuous and one categorical). My response variable is also continuous.
When I attempt to run this model the following error appears:
Warning message: In fitTMB(TMBStruc) : Model convergence problem; non-positive-definite Hessian matrix. See vignette('troubleshooting')
I've tried looking at vignette('troubleshooting') to solve the problem however I am still relatively new to R and statistics in general so am not really sure how to proceed in fixing the problem. Any help would be greatly appreciated.