siar needs to die as a package... we really need to form a sensible plan for this... either replace with simmr, or call simmr siar v5.0 and write up a new package description for publication somewhere... easier with a new name, but really places like Methods in Ecology and Evolution should take major version updates too.
Spend some time in practical sessions going through the correct format for data for analysis by the various packages. This isn't helped at all by the myriad formats the various packages need the data in.... e.g. different packages, and then different files within each package.
One might even conceive a single common format for the data, to create an overall new SIMM object that can be coerced by various helper functions in siar, mixsiar, simmr, and siber to convert it accordingly for analysis within each... maybe...