Testing Rmd to md using knitr

August 6, 2016   

I use Rmarkdown a lot. I have recently been preparing lecture notes using it and I wanted to see how easy it would be for me take an Rmarkdown document and create a blog post.

Firstly, this whole website is built using Jekyll which means that I need each of my blog posts to start with the date and then the title. For instance this blog post came from a file named 2016-08-26-Testing-Rmd-to-md-using-knitr.Rmd. I then need to create a markdown (or html file) of the same name. This is no problem with the R package knitr. All we need to do is

{% highlight r %} knit(“2016-08-26-Testing-Rmd-to-md-using-knitr.Rmd”) {% endhighlight %}

and it’ll convert to .md. For Jekyll this needs to end up in a folder named _posts and any figures need to be placed where they can be accessed. To take care of this I put them in my images folder.

To do all this automatically I wrote this script which always re-knits all my Rmd blog posts.

{% highlight r %}

Script to knitr all the Rmd files into md blog posts.

load package

library(knitr)

delete all previous figures

file.remove(dir( path = “images/figs/”, full.names = TRUE ))

set base url for links

opts_knit$set(base.url = ‘/’, base.dir = getwd())

Setting directory for figures

opts_chunk$set(fig.path = “images/figs/”) opts_chunk$set(fig.cap = “center”)

get all filenames

filenames = list.files(“Rmd/”, pattern = “*.Rmd”) num_files = length(filenames)

for (i in c(1:num_files)) { # split the blog title from the .Rmd file so we can create the .md blog file blog_title = unlist(strsplit(filenames[i], “[.]“))[1] knit(input = paste(“Rmd/”, filenames[i], sep = “”), output = paste(”_posts/“, blog_title, “.md”, sep = “”)) } {% endhighlight %}

Just so we can see what plots look like I’ve included the default demo from an Rmarkdown document.

{% highlight r %} plot(pressure) {% endhighlight %}

center