merDeriv is a free, open source R package for computing derivatives of mixed models estimated via lme4. Allows users to compute scores (casewise/clusterwise first derivatives of likelihood function) and variance-covariance matrix of all estimated parameters, including random effect (co)variances. The authors acknowledge support from NSF grant 1460719. The contents of this package are those of the authors and do not reflect the views of the National Science Foundation.
For further information, see:
Wang, T. & Merkle, E. C. (2018). Derivative Computations and Robust Standard Errors for Linear Mixed Effects Models in lme4. Journal of Statistical Software, 87(1), 1-16. DOI: 10.18637/jss.v087.c01