Version Control and Reproducible Research/Data Science

A current hot-topic in research, especially within statistically driven or based research is “reproducible research”. In academia, the process of peer-review publication is meant to assure that any finding are reproducible by other scientists. But those of us in the trenches, and especially on the data-side of things know that is a theoretical outcome (the reproduciblity) and far more rarely something tested. While academia is rightly under fire for this lack of actual, reproducible research (see this great example from epidemiology) this is even more of a problem in industry. If the analysis can’t be reproduced, then it can’t be applied to new client base.

So why bring this up on a educational blog? I think its important to embed the idea of reproducible work deep inside our teaching and assignment practices. While the idea of repeating a specific analysis once the data has changed isn’t really novel, it becomes far more relevant when we begin talking about filtering or cleaning the input data. Just think about searching for outliers in a data-set. First, we might plot a histogram of values/categories, then we go back, remove the data points that we want ignored, and replot the histogram. BAM! The we have a perfect opportunity to teach the value of reproducible work! We used exactly the same visualization technique (a histogram), on practically the same data (with outliers and without outliers).

Where does the reproduction of the work fit in though? Python and R both have histogram functions, so this is definitely a toy example (but the whole idea of functions can serve to emphasize the idea of reproducible/reusable work). Instead, I think this is where the instructor has an opportunity. This idea of cleaning outliers could easily be demonstrated in the command line window of R or an interactive Python shell. And then you’ve lost your teaching moment. Instead, if this is embedded in an R script or Python/R Notebook you can reuse the code, retrace whatever removal process you used, etc. In the courses I’ve taught, I’ve seen student after student complete these sorts of tasks in the command-line window, especially when told to do so as part of an active, in-class demo. But they never move the code into a script so when they are left to their own devices they flounder and have to go look for help.

I titled this post “Version Control and Reproducible Research” … you might be wondering what version control has to do with this topic. The ideas described above are great if you are the sole purveyor of your code/project. But if you have your students working in teams, or are trying to collaborate yourself, this might not be exactly ideal. But it’s getting pretty close! Here’s the last nugget you need to make this work… version control. Or in this case, I’m specifically talking about using GitHub. The short version of what could be an entire separate post (I’ll probably try to do one eventually) is that git (and the cloud repository github) is the tool that software developers designed to facilitate collaborative software development without the desire to kill each other from broken code. It stores versions of code (or really any file) that can be jointly contributed to without breaking each other’s work. For now, I’ll point you to a few resources on this..

First, a bit more from an industry blog on workflows to promote reproduction using github — Stripe’s Notebooks and Github Post

Second, for using Git/GitHub with R — Jenny Bryan, Prof. University of British Columbia — Note that this is a really long, complete webpage/workshop resource!

Third, a template/package for Python to help structure your reproducible git-hub work — Cookiecutter Data Science —  (heck, this could be an entire lesson itself in how to manage a project– more on that later)

Fourth, a template/package for R to help structure your reproducible git-hub/R work — ProjectTemplate

 

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