Calling R From Julia

Josh Day -

Since Julia has a younger ecosystem, you won't always find the functionality you need for every task.  In those cases, you're left with the choice to either

Particularly for niche models in the field of statistics, you'll often find R packages that do not have Julia counterparts.  Thankfully, Julia and R work together seamlessly through the help of one package.

Introducing RCall.jl

To get started, let's install RCall:

] add RCall

Running R Code from Julia

  • After installing and typing using RCall, you'll have access to the R REPL Mode by typing $.  Your prompt will change from julia> to R>  and now all of your commands will run in R instead of Julia.  You can use it just like a normal R session.
julia> using RCall

# type `$`

R> install.packages("ggplot2")

R> library(ggplot2)

R> data(diamonds)

R> ggplot(diamonds, aes(x=carat, y=price)) + geom_point()
  • If you want to call R from Julia in a non-interactive manner (not from the REPL), you can use @R_str macro:
julia> R"y = 2"
RObject{RealSxp}
[1] 2

Sending Julia Variables to R

  • The @rput macro sends a variable to R and uses the same name.
julia> x = 1
1

julia> @rput x
1

R> x
[1] 1
  • You can interpolate Julia values in @R_str commands as well as the R REPL Mode:
julia> x = 1
1

julia> R"y = $x"
RObject{IntSxp}
[1] 1

R> 1 + $x
[1] 2

Retrieving R Variables in Julia

  • The @rget macro sends a variable from R to Julia and uses the same name.
julia> R"z = 5"
RObject{RealSxp}
[1] 5


julia> @rget z
5.0

julia> z
5.0
  • You can also convert an RObject into the appropriate Julia counterpart with rcopy.
julia> robj = R"z"
RObject{RealSxp}
[1] 5


julia> rcopy(robj)
5.0

🚀 That's It!

You now know the basics of working in R from Julia.  There are deeper depths to dive into on the topic (such as type conversions between R and Julia), but this should give you a start on using your favorite R package together with Julia.

Enjoying Julia For Data Science?  Please share us with a friend and follow us on Twitter at @JuliaForDataSci.

Additional Resources