[R] Best way to study internals of R ( mix of C, C++, Fortran, and R itself)?

[Robert Wilkins]

How difficult is it to get a good feel for the internals of R, if you want
to learn the general code base, but also the CPU intensive stuff ( much of
it in C or Fortran?) and the ways in which the general code and the CPU
intensive stuff is connected together?

R has a very large audience, but my understanding is that only a small
group have a good understanding of the internals (and some of those will
eventually move on to something else in their career, or retire
altogether).

While I'm at it, a second question: 15 years ago, nobody would ever offer a
job based on R skills ( SAS, yes, SPSS, maybe, but R skills, year after
year, did not imply job offers). How much has that changed, both for R and
for NumPy/Pandas/SciPy ?

thanks in advance

Robert

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