R Package multgee: A Generalized Estimating Equations Solver for Multinomial Responses

This introduction to the R package multgee is a slightly modified version of ?, published in the Journal of Statistical Software. To cite multgee in publications, please use ?. To cite the GEE methodology implemeted in multgee, please use ?. The R package multgee implements the local odds ratios generalized estimating equations (GEE) approach proposed by ?, a GEE approach for correlated multinomial responses that circumvents theoretical and practical limitations of the GEE method. A main strength of multgee is that it provides GEE routines for both ordinal (ordLORgee) and nominal (nomLORgee) responses, while relevant softwares in R and SAS are restricted to ordinal responses under a marginal cumulative link model specification. In addition, multgee offers a marginal adjacent categories logit model for ordinal responses and a marginal baseline category logit model for nominal. Further, utility functions are available to ease the local odds ratios structure selection (intrinsic.pars) and to perform a Wald type goodness-of-fit test between two nested GEE models (waldts). We demonstrate the application of multgee through a clinical trial with clustered ordinal multinomial responses.