Extendr is available on crates.io.

Simply add this line to the [dependencies] section of a rust crate. You will then be able to call R code from Rust.

[dependencies]
extendr-api = "0.2"

Installation - R

There are two ways you can use the extendr API from R. First, you can use the rextendr package to call individual Rust functions from an R session. Second, you can write an R package that uses compiled Rust code, see the helloextendr repo for a minimal example.