Julia in RMarkdown

Changcheng Li

2018-05-01

Use JuliaCall as Julia Engine in R Markdown

To use JuliaCall package for julia engine in R Markdown document. Just set the engine for julia to JuliaCall::eng_juliacall like this:

knitr::opts_chunk$set(echo = TRUE)
knitr::knit_engines$set(julia = JuliaCall::eng_juliacall)

Below is how it looks like when using JuliaCall as language engine for Julia.

How Does JuliaCall in R Markdown Look Like?

## This is a julia language chunk.
## In julia, the command without ending semicolon will trigger the display
## so is JuliaCall package. 
## The julia display will follow immediately after the corresponding command
## just as the R code in R Markdown.
a = sqrt(2)
## 1.4142135623730951
a = sqrt(2);

## And lots of different types of display are supported in JuliaCall.
## Like markdown and plots.
@doc sqrt
## ```
## sqrt(x)
## ```
## 
## Return $\sqrt{x}$. Throws [`DomainError`](@ref) for negative [`Real`](@ref) arguments. Use complex negative arguments instead. The prefix operator `√` is equivalent to `sqrt`.

Support for Plots.jl

Plots.jl is an easy to use and powerful julia package for plotting, https://github.com/JuliaPlots/Plots.jl. And JuliaCall supports Plots.jl of course!!

PyPlot backend

## Plots.PyPlotBackend()

GR backend

## Plots.GRBackend()

Get Access to Julia in R Chunk

And you can also get access to julia variables in R code chunk quite easily using JuliaCall, for example:

library(JuliaCall)
## This is a R language chunk.
## In the previous julia chunk, we define variable a, 
## we can use functions in JuliaCall to get access to it.
julia_eval("a")
## [1] 1.414214