It is common to have the same figure used in multiple places among articles, beamer slides, and posters. Therefore, it is desired to share the TikZ source codes without duplicating the files. Noted, the figures used in the beamer often contain the animations in the form of \onslide<overlay specification>{...}. As such, we need to a way to manage these differences in the TikZ source codes and avoid the duplication at the same time.

To tackle this issue, I found a nice solution is to use the standalone package. As its name suggests, it can be used to create pictures as standalone or as part of a document. For example, we can create a figure as the following:

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\documentclass[tikz]{standalone}

\usetikzlibrary{calc,positioning}

% Create fake \onslide and other commands for standalone picture
\usepackage{xparse}
\NewDocumentCommand{\onslide}{s t+ d<>}{}
\NewDocumentCommand{\only}{d<>}{}
\NewDocumentCommand{\uncover}{d<>}{}
\NewDocumentCommand{\visible}{d<>}{}
\NewDocumentCommand{\invisible}{d<>}{}

\begin{document}

\begin{tikzpicture}
  \node[draw] (start) { Start };
  \node[draw, right=2cm of start] (end) { End };
  % The following animation will only have affect in beamer.
  % In standalone mode, the figure is static.
  \onslide<2-> { \draw[-latex] (start) -- (end); }
  \coordinate (mid) at ($(start)!.5!(end)$);

  % We could control parts of figure only shown in beamer or vice versa.
  \ifstandalone
    \node[below=1cm of mid] {Only Shown in Standalone Figure};
  \else
    \node[below=1cm of mid] {Only Shown in Beamer};
  \fi
\end{tikzpicture}

\end{document}

This file can be compiled directly to create standalone picture, which could be helpful if you want to create image used by web pages or other similar scenarios. To include this figure in the article or poster, you can use standalone package in the following manner:

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\documentclass{article}

% `mode=build` tells LaTeX to build the image from the source then use it.
\usepackage[mode=build]{standalone}

\begin{document}

\begin{figure}[t]
  \centering
  \includestandalone[width=0.8\linewidth]{./figure} % without the `.tex` extension
  \caption{TikZ Figure in Article}
\end{figure}

\end{document}

Finally, this figure can be used in beamer with its animations functioning as normal.

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\documentclass{beamer}

% `mode=tex` means we will use the source file of the figures directly.
\usepackage[mode=tex]{standalone}

% We need to add TikZ definitions again. You could put them in a separated file
% and use `\input{...}` command to avoid the duplication.
\usepackage{tikz}
\usetikzlibrary{calc,positioning}

\begin{document}

\begin{frame}{TikZ Figure in Beamer}
  \begin{figure}
    \centering
    \includestandalone[width=0.8\linewidth]{./figure} % without the `.tex` extension
  \end{figure}
\end{frame}

\end{document}

Note: In order to use mode=build, you need to pass -shell-escape flag to the LaTeX compiler. Further, for latexmk users, mode=buildnew is preferred than mode=build. Otherwise, latexmk could be stuck in a loop of compiling the files repeatedly.

First, you need to install Ruby and the mail library. You can install the library by gem install mail.

Second, since there are lots of emails to be sent, it is a better idea to maintain a single SMTP connection to the email server to reduce the overhead. This is also beneficial to avoid possible network issues. You can open an SMTP connection using following Ruby codes, which connects to the email server in my department.

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require "mail"
require "socket"

smtp_conn = Net::SMTP.new("mh2.comp.hkbu.edu.hk", 465)
smtp_conn.set_debug_output $stderr
smtp_conn.enable_tls
smtp_conn.start Socket.gethostname, "<username>", "<password>", "login"

Mail.defaults do
  delivery_method :smtp_connection, connection: smtp_conn
end

Finally, format your emails and deliver them. It is worth noting that you should sleep a few seconds between each email delivering to avoid DoSing the email server.

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# format the email
mail = Mail.new do
  from     'from@example.com'
  to       'to@example.com'
  subject  '<subject>'
  body     '<body>'
  add_file filename: 'some_attachment.txt', content: File.read('/path/to/attachment.txt')
end

# check the email
puts mail

# send the email
mail.deliver!

sleep 2 # wait a bit
# handle next email

There are many approaches to install R and the knitr package. Below are two possible ways.

• Install R using your favorite package manager or directly from the official website. And install knitr by running install.packages('knitr', dependencies = TRUE) in the R prompt.
• Install R using Anaconda by running conda install -c r r-essentials in the shell. It will install R along with some most common used R libraries including the knitr. This approach is especially beneficial under the Windows operating system.

Based on your favorite editor, different configuration can be implemented to setup for automatically and continues LaTeX compiling. You may refer to this blog for more information. However, what is missing is how to compile LaTeX with R (knitr) using latexmk, which is one of the most widely used tools to compile LaTeX document and is supported by almost all of LaTeX editors.

Therefore, I wrote up below piece of code to allow latexmk work with the knitr files (.Rnw or .Rtex) seamlessly. You could append them in your global ~/.latexmkrc file or local .latexmkrc under the project root.

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# only enable when compiling .Rnw or .Rtex file
if(grep(/\.(rnw|rtex)$/i, @ARGV)) {
    $latex = 'internal knitrlatex ' . $latex;
    $pdflatex = 'internal knitrlatex ' . $pdflatex;
    my $knitr_compiled = {};
    sub knitrlatex {
        for (@_) {
            next unless -e $_;
            my $input = $_;
            next unless $_ =~ s/\.(rnw|rtex)$/.tex/i;
            my $tex = $_;
            my $checksum = (fdb_get($input))[-1];
            if (!$knitr_compiled{$input} || $knitr_compiled{$input} ne $checksum) {
                my $ret = system("Rscript -e \"knitr::knit('$input')\"");
                if($ret) { return $ret; }
                rdb_ensure_file($rule, $tex);
                $knitr_compiled{$input} = $checksum;
            }
        }
        return system(@_);
    }
    # clean up generated .tex file when running `latexmk -c <root_file>`
    $clean_ext .= ' %R.tex';
}

For me, it works nicely under vim with the vimtex plugin. Just name the file with .Rnw extension, and edit and compile it like normal LaTeX file.

Personal, I found pry is much more power than irb. For example, Gregg Rothmeier wrote this blog to show some useful features pry provided. In addition, pry ships with the support of plugin system.

So, how to use pry as the front end of interactive Homberew shell? I wrote a piece of code as shown below. Put it in the file brew-pry and make sure it has execute attribute and can be found in the PATH. That’s it. Run brew pry to use pry in Homebrew shell.

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#!/usr/bin/env ruby

$:.unshift ENV["HOMEBREW_LIBRARY_PATH"]
require "global"
require "formula"
require "keg"
require "pry"

class Symbol
  def f(*args)
    Formulary.factory(to_s, *args)
  end
end
class String
  def f(*args)
    Formulary.factory(self, *args)
  end
end

if ARGV.include? "--examples"
  puts "'v8'.f # => instance of the v8 formula"
  puts ":hub.f.installed?"
  puts ":lua.f.methods - 1.methods"
  puts ":mpd.f.recursive_dependencies.reject(&:installed?)"
else
  ohai "Interactive Homebrew Shell"
  puts "Example commands available with: brew pry --examples"
  Pry.start
end

Update (2015/2/16)

I found using HOMEBREW_LIBRARY_PATH to locate Homebrew library path is a better idea. This can be useful if you have multi Homebrew in your system.

• Markdown Support: I use Jekyll and markdown to write the blogs. So the render should be integrated to this system seamlessly. Moreover, it should be able to:
  • Use LaTeX code directly in the markdown without any other HTML/JavaScript notion. For example, $$ E = mc^2 $$ should be rendered to $E = mc^2$ automatically.
  • Work in default Github Page environment. I want to use Github Page to automatically generate the site. And due to the security reason, Github doesn’t allow running custom plugins for Jekyll. Therefore, the rendering shouldn’t depend any non-default plugin or markdown parser.
• Quality: Quality is important. The render needs to be fast and output print quality typesetting.

The most popular way to render LaTeX within Jekyll is using MathJaX. There are lots of blogs (e.g. this) to show you how to configure it. But MathJaX has a huge shortage on rendering speed. It’s slow, not for a bit, but so slow that you can see the web page refreshing itself.

Recently, I came across a new project KaTeX. It’s fast as you can see the comparison below in which KaTeX is on the left and MathJax is on the right.

So how to make KaTeX work in the Jekyll? Will Drevo offers a comprehensive manual to make it work. However, it requires us to write LaTeX code inside HTML div block. And I found this blog to explain how to use KaTeX with JavaScript. Combining both of these works, and with some extra effort, I find the approach to use KaTeX seamlessly inside Jekyll.

First of all, we need to configure Jekyll using Kramdown as markdown parser and MathJax as Kramdown’s math engine. In result, inline math equation will be rendered into a script block with “math/tex” as type. Like this: <script type="math/tex"> tex code </script>. Similarly the display style math equation will turn into a script block with “math/tex; mode=display” as type. Like this: <script type="math/tex; mode=display"> tex code </script>.

Secondly, let us put the required resources into the HTML head.

Finally, with the power of jQuery and KaTeX, we replace all the TeX code block to rendered high quality equations fast. But remember, this JavaScript should be loaded at the end of HTML file.

Here’s the final result of rendered equation in below. Also you can do whatever custom you want in CSS file using class inline-equation and equation.