Circadian/cosinor analysis - help

Hello,

Does anyone here know how to analyse circadian data? I am confused on how to use the Cosinor function in R, or even whether plotting the LS-means and then using ANOVA is the best way to go? I am only investigating the rhythmicity of an immune protein, but I also want to compare 3 different groups.

Any help would be amazing!

Best,
Sam