Analyzing positive data with 0 values can be challenging, since a direct log transformation isn't possible. I discuss some of the things to consider when deciding on an analysis strategy for such data and then explore the effect of the value of the constant, c, when using log(y + c) as the response variable.
Checking for model fit from generalized linear mixed models (GLMM) can be challenging. The DHARMa package helps with this by giving simulated residuals but doesn't work with all model types. I show how to use tools in DHARMa to extend it for use with unsupported models fit with glmmTMB() and zeroinfl().