User-definable parameters for all functions. Notably: period can be estimated rather than always user-defined, rhythmic characteristics can be selectively shared between groups, all parameters can have additional decay terms and those decay terms can have group-effects to determine differences in decay between groups.
More informative summary tables from all models.
More sensible default values for random effects.
nlme is used for estimating presence of rhythmicity of each group when circacompare_mixed() is used, rather than nls.