Andrew B. Collier / @datawookie

Your code won’t be terribly interesting without ways of getting data in and out. Ways to do that with Julia will be the subject of today’s post.

Console IO

Direct output to the Julia terminal is done via print() and println(), where the latter appends a newline to the output.

julia> print(3, " blind "); print("mice!\n")
3 blind mice!
julia> println("Hello World!")
Hello World!

Terminal input is something that I never do, but it’s certainly possible. readline() will read keyboard input until the first newline.

Yesterday I had a look at Julia’s support for Functional Programming. Naturally it also has structures for conventional program flow like conditionals, iteration and exception handling.

An earlier post looked at how to work with functions in Julia. This time we’ll dig into Functional Programming, an approach to coding which, not surprisingly, depends on writing functions.

Julia performs Just-in-Time (JIT) compilation using a Low Level Virtual Machine (LLVM) to create machine-specific assembly code. The first time a function is called, Julia compiles the function’s source code and the results are cached and used for any subsequent calls to the same function. However, there are some additional wrinkles to this story.

The previous post considered a selection of development environments for working with Julia. Now we’re going to look at a topic which is central to almost every programming task: variables.

Most coding involves the assignment and manipulation of variables. Julia is dynamically typed, which means that you don’t need to declare explicitly a variable’s data type. It also means that a single variable name can be associated with different data types at various times. Julia has a sophisticated, yet extremely flexible, system for dealing with data types. covered in great detail by the official documentation. My notes below simply highlight some salient points I uncovered while digging around.

As a long-term R user I’ve found that there are few tasks (analytical or otherwise) that R cannot immediately handle. Or be made to handle after a bit of hacking! However, I’m always interested in learning new tools. A month or so ago I attended a talk entitled Julia’s Approach to Open Source Machine Learning by John Myles White at ICML in Lille, France. What John told us about Julia was impressive and intriguing. I felt compelled to take a closer look. Like most research tasks, my first stop was the Wikipedia entry, which was suitably informative.

Reading Bayesian Computation with R by Jim Albert (Springer, 2009) inspired a fit of enthusiasm. Admittedly, I was on a plane coming back from Amsterdam and looking for distractions. I decided to put together a Shiny app to illustrate successive Bayesian updates. I had not yet seen anything that did this to my satisfaction. I like to think that my results come pretty close.

As an aside for a Social Media Automation project I have constructed a bot which uses data from the World Wide Lightning Location Network (WWLLN) to construct daily animated maps of global lightning activity and post them on my Twitter feed. The bot runs remotely and autonomously on an EC2 instance.

Word clouds have become a bit cliché, but I still think that they have a place in giving a high level overview of the content of a corpus. Here are the steps I took in putting together the word cloud for the International Conference on Machine Learning (2015).

Sundry notes from the fourth day of the International Conference for Machine Learning (ICML 2015) in Lille, France. Some of this might not be entirely accurate. Caveat emptor.

Celeste: Variational inference for a generative model of astronomical images (Jeffrey Regier, Andrew Miller, Jon McAuliffe, Ryan Adams, Matt Hoffman, Dustin Lang, David Schlegel, Prabhat)

Colour modelled as a 4 dimensional vector. The Physics (Planck’s Law) places some constraints on the components of these vectors. Light density model accounts for rotation as well as asymmetry of galactic axes.

Selected scribblings from the third day at the International Conference for Machine Learning (ICML 2015) in Lille, France. I’m going out on a limb with some of this, since the more talks I attend, the more acutely aware I become of my limited knowledge of the cutting edge of Machine Learning. Caveat emptor.

Adaptive Belief Propagation (Georgios Papachristoudis, John Fisher)

Belief Propagation describes the passage of messages across a network. The focus of this talk was Belief Propagation within a tree. The authors consider an adaptive algorithm and found that their technique, AdaMP, was significantly better than the current state of the art algorithm, RCTreeBP.

Some notes from the second day at the International Conference for Machine Learning (ICML 2015) in Lille, France. Don’t quote me on any of this because it’s just stuff that I jotted down during the course of the day. Also much of the material discussed in these talks lies outside my field of expertise. Caveat emptor.

Two Big Challenges in Machine Learning (Léon Bottou)

Machine Learning is an Exact Science. It’s also an Experimental Science. It’s also Engineering.

Started the day with a run through the early morning streets of Lille. This city seems to wake up late because it was still nice and quiet well after sunrise. Followed by a valiant attempt to sample everything on the buffet breakfast. I’ll know where to focus my attention tomorrow.

ICML2015

The first day of the International Conference on Machine Learning (ICML 2015) in Lille consisted of tutorials in two parallel streams. Evidently the organisers are not aware of my limited attention span because these tutorials each had nominal durations of longer than 2 hours, punctuated by a break in the middle.

“Machine Learning with R Cookbook” by Chiu Yu-Wei is nothing more or less than it purports to be: a collection of 110 recipes for applying Data Analysis and Machine Learning techniques in R. I was asked by the publishers to review this book and found it to be an interesting and informative read. It will not help you understand how Machine Learning works (that’s not the goal!) but it will help you quickly learn how to apply Machine Learning techniques to you own problems.