I found the dependencies, I think, by locating the registry (] registry status) and looking at the General\R\RCall\Compat.toml file which appears to have sections labelled with releases of RCall and required versions for the dependencies. In particular, it has
["0.13.4-0"]
DataFrames = "0.19.0-*"
StatsModels = "0.6"
for the lastest version. Earlier than that the StatsModel dependency specified for
["0.10.6-0.13.3"]
StatsModels = "0.2.4-0.5"
applies. So the only version consistent with my StatsModels is the most recent one.
However, my DataFrames were from the past:: 0.18.3, and thus not compatible with the latest RCall which requires 0.19 or higher… So no version of RCall was consistent with both installed versions.
I did a package update, bringing my DataFrames to 0.19.4, among other changes. I also did a git update for my dev’d StatsModels, taking it from 0.6.0 to 0.6.5.
After these steps ] add RCall succeeded.
Granted that the compatibility problems I encountered may be a bit tricky to summarize–though how about
Your environment’s StatsModels v0.18.3 requires RCall v0.13.4, but your environment’s DataFrames v 0.18.3 requires RCall v0.13.3. Impossible to satisfy.
–but the messages printed could be clearer, and ideally more helpful.
Even more generally, there doesn’t seem to be a way of discovering the dependency and versioning info except looking in the files. Given that each version of a a project may have a distinct set of dependencies things get complicated quickly.