Julia with Emacs Org mode


This post details how to use Emacs Org mode to create Julia notebooks and to perform HTML or PDF exports. I tried to get the simplest working solution.

Julia notebook functionality works out of the box thanks to ob-julia.el and this is what I am using instead of Jupiter notebooks. However, the solution to export HTML and PDF is not straightforward.

I wanted to:

  • have nice Julia code snippets with full UTF8 supports,
  • being able to export in both HTML and PDF, including bibliography.

I get a solution which is certainly not perfect, ideas to improve it are welcomed.

There are two points to take care of:

  • LaTeX does not fully support UTF8, nor its listings package.
    • for UTF8 support I had to switch to luatex, biber and minted package
    • I also had to use proper fonts, DejaVu, to support Greek letters and mathematical symbols.
  • to make the bibliography exportable in both HTML and PDF without .org file modification, I had to use a little trick.

The proposed solution uses:

  • ob-julia.el : to support notebook functionality,
  • ox-bibtex.el : used for html-export of the bibliography, requires bibtex2html (Debian package),
  • luatex : under Debian, included in the texlive-latex-base package,
  • biber : under Debian, the biber package,
  • pygments : under Debian, the python-pygments package. Attention with python3-pygments, it does not on my computer. I have not investigated this.

Maybe I have forgotten something, just tell me (I am only using Linux).

There is a GitHub repository to reproduce results of this post. The example.pdf generated file is also present.

Emacs configuration

Getting ob-julia.el and ox-bibtex.el

You can found ob-julia.el and ox-bibtex.el in Org-mode Contributed Packages. Easy download can be performed using:

curl -o emacs_files/ob-julia.el https://code.orgmode.org/bzg/org-mode/raw/master/contrib/lisp/ob-julia.el
curl -o emacs_files/ox-bibtex.el https://code.orgmode.org/bzg/org-mode/raw/master/contrib/lisp/ox-bibtex.el

Minimal init.el file

This is a minimal configuration to reproduce the results. The code with its comments is self-explaining:

;; Use your own packages for classical stuff
;; requires Emacs speaks statistics, Org
(require 'ess-site)
(require 'org)

;; removes ugly horizontal lines in html-exported code 
;; (not mandatory)
(setq org-html-keep-old-src t)

;; As ob-julia.el and ox-bibtex are less common, 
;; we use a local repository.
;; Usage: emacs -q --load emacs_files/init.el
;; In a more usual setting one should use:
;; (require 'ob-julia.el)
;; (require 'ox-bibtex)
(load-file "emacs_files/ob-julia.el") ; works with ess-site, our notebook engine
(load-file "emacs_files/ox-bibtex.el"); used for bibliography HTML-export 

;; allows julia src block (requires ob-julia.el)
(setq org-confirm-babel-evaluate nil)

 '((julia . t)))

;; defines image width in the OrgMode buffer (this is not for html
;; exports, for this you must use #+HTML_ATTR: :width 900px for
;; instance)
;; This is not mandatory, but useful when one uses the gr() Plots.jl
;; backend as it exports wide .png files. CAVEAT: use imagemagick for
;; image resizing.
(setq org-image-actual-width (/ (display-pixel-width) 4))

;; uses the minted package instead of the listings one
(setq org-latex-listings 'minted)

;; defines how to generate the pdf file using lualatex + biber
(setq org-latex-pdf-process
      '("lualatex -shell-escape -interaction nonstopmode -output-directory %o %f"
        "biber %b"
        "lualatex -shell-escape -interaction nonstopmode -output-directory %o %f"
        "lualatex -shell-escape -interaction nonstopmode -output-directory %o %f"))

.org file configuration

For demonstration purpose we define an .org file example. This file is kept very simple to do not distract from the required configuration part.

LaTeX directives

We have the LaTeX configuration part:

# uses minted package instead of listings 
#+LATEX_HEADER: \usepackage{minted}    

# uses fonts to support Greek letters etc...
#+LATEX_HEADER: \usepackage{fontspec}
#+LATEX_HEADER: \setmonofont{DejaVu Sans Mono}[Scale=MatchLowercase]

# defines the \begin{comment} \end{comment} environment, used to avoid
# conflict between bibtex and biblatex
#+LATEX_HEADER: \usepackage{verbatim} 

# uses the biblatex package (and not the old bibtex) 
#+LATEX_HEADER: \usepackage[backend=biber, bibencoding=utf8 ]{biblatex}
# our bibliography file
#+LATEX_HEADER: \addbibresource{my-bib.bib}

We then define our the Julia code highlight style. This style is used by minted for PDF export.


Our notebook

Now this is the beginning of our notebook. One can use Org as usual…

#+TITLE: My title
#+AUTHOR: author

* Very simple demo

#+BEGIN_SRC julia  :eval no-export :session *demo_session* :exports none
using Plots

** UTF8 support + escape math equation
Note that UTF8 is supported (the \alpha variable) :

#+BEGIN_SRC julia :eval no-export :session *demo_session* :exports both :results silent :wrap "SRC julia :eval never"
# Generate a matrix $a_{i,j}=\mathcal{U}([0,1[)$

** Long lines are wrapped

#+BEGIN_SRC julia :eval no-export :session *demo_session* :exports both :results output :wrap "SRC julia :eval never"
function ⊗(a::AbstractArray{T},b::AbstractArray{S}) where {T<:Number,S<:Number} kron(a,b) end;

γ = α ⊗ β

** Plot example

You can easily generate plots, one example from [[http://docs.juliaplots.org/latest/examples/pyplot/][Plots Julia package]],
 is used to generate Figure [[PolarPlot]].

#+BEGIN_SRC julia  :eval no-export :session *demo_session* :exports code :results silent
Θ = linspace(0,1.5π,100)
r = abs(0.1 * randn(100) + sin.(3Θ))

#+BEGIN_SRC julia  :eval no-export :session *demo_session* :results graphics :file example.png :exports results

#+CAPTION: A polar plot.
#+ATTR_HTML: :width 900px
#+NAME: PolarPlot

** Org with bibliography

{\frac {d}{dt}}\iint _{\Sigma (t)}\mathbf {F} (\mathbf {r} ,t)\cdot d\mathbf {A} = & \iint _{\Sigma (t)}\left(\mathbf {F} _{t}(\mathbf {r},t)+\left[\nabla \cdot \mathbf {F} (\mathbf {r} ,t)\right]\mathbf {v}
\right)\cdot d\mathbf {A} - \\
& \oint _{\partial \Sigma (t)}\left[\mathbf{v} \times \mathbf {F} (\mathbf {r} ,t)\right]\cdot d\mathbf {s} \nonumber

Eq. \ref{eq:one_eq} is demonstrated in cite:Flanders1973.


Now we reach a little trick to support both HTML and PDF bibliography exports:


#+BIBLIOGRAPHY: my-bib plain


To export HTML bibliography, ox-bibtex does the job with only one directive:

#+BIBLIOGRAPHY: my-bib plain

However, for PDF export we do not want to use ox-bibtex, as it does not support UTF8. The solution is to wrap this directive into a comment section in the generated .tex code:

#+BIBLIOGRAPHY: my-bib plain

Now we must tell LaTeX to use biblatex, this is done thanks to this directive:


Putting everything together you get the proposed solution. This is certainly not the cleanest approach, but I have not found simpler.

The my-bib.bib file

For our example we need a small bibliography my-bib.bib file:

  doi = {10.2307/2319163},
  url = {https://doi.org/10.2307/2319163},
  year  = {1973},
  month = {jun},
  publisher = {{JSTOR}},
  volume = {80},
  number = {6},
  pages = {615},
  author = {Harley Flanders},
  title = {Differentiation Under the Integral Sign},
  journal = {The American Mathematical Monthly}


You can visit the GitHub repo to reproduce the results.

Starting Emacs with the local configuration

From project root directory type

emacs -q --load emacs_files/init.el

to start a new Emacs with our local configuration.

Recomputing the notebook

As I potentially have several notebooks to publish I have used the :eval no-export argument. By consequence the notebooks are not evaluated each time you publish but only once. If you want to recompute everything every time, simply remove this option. You can also use the :cache option.

By consequence, before exporting you must begin by a first evaluation of the notebook. Visit the example.org buffer and do M-x org-babel-execute-buffer (or use the C-c C-v b shortcut). Attention, be sure that Plots.jl is installed.

ERROR: MethodError: no method matching start(::…)

In the ∗demo_session∗ Julia session buffer you will certainly see this error:

ERROR: MethodError: no method matching start(::...)

This is not our fault, but a known problem (that would need a fix) julia-print-commands-not-working-in-emacs-org-mode. It does not affect the computed result (but only the output processing). To get the right output (without the error message) one workaround is to restart computation of the source block (C-c C-c).


Still from the example.org buffer, you can do:

  • HTML export with: C-c C-e h o
  • PDF export with: C-c C-e l o

This should generate and open fresh hmtl and pdf files.

Note: concerning html files, this is a basic export, you can use your own HTML theme.


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