Linking R and Julia?

The Julia development plan, as I described in this answer is to allow compilation of Julia code to shared libraries, callable using the C ABI. Once this happens, it will be as easy to call Julia code from R as it is to call C/C++ code. There is, however, a fair amount of work required before this becomes possible.

I too have been looking at Julia ever since Doug Bates sent me a heads-up in January. But like @gsk3, I measure this on an "Rcpp scale" as I would like to pass rich R objects to Julia. And that does not seem to be supported at all right now.

Julia has a nice and simple C interface. So that gets us something like .C(). But as recently discussed on r-devel, you really do not want .C(), in most cases you rather want .Call() in order to pass actual SEXP variables representing real R objects. So right now I see little scope for Julia from R because of this limitation.

Maybe an indirect interface using tcp/ip to Rserve could be a first start before Julia matures a little and we get a proper C++ interface. Or we use something based on Rcpp to get from from R to C++ before we enter an intermediate layer [which someone would have to write] from which we data feed to Julia, just like the actual R API only offers a C layer. I don't know.

And the end of the day, some patience may be needed. I started to look at R around 1996 or 1997 when Fritz Leisch made the first announcements on the comp.os.linux.announce newsgroup. And R had rather limited facilities then (but the full promise of the S language, of course, si we knew we had a winner). And a few years later I was ready to make it my primary modeling language. At that time CRAN had still way less than 100 packages...

Julia may well get there. But for now I suspect many of us will get work done in R, and have just a few curious glimpses at Julia.

The RJulia R package looks quite good now from R. R CMD check runs without warnings or errors (if julia is properly installed).

Biggest TODO in my view is to get Julia to return named lists which constitute the really basic flexible general data structure in R.

Note that Doug Bates alerted me about RCall a bi-directional interface from Julia to R (i.e., the other direction than R to Julia). Also, Doug recommended to target julia 0.4.0 rather than the current stable versions of julia.

Several more interfaces have appeared since the above was written: Now (2021-04), we've got R packages

• JuliaCall (~2017) which embeds Julia in R, and is actively maintained available from CRAN.
• JuliaConnectoR (~2019), also available from CRAN which aims even higher, e.g., directly importing julia objects into R