Category Archives: programming

Some basics of biomaRt

One of the commonest bioinformatics questions, at Biostars and elsewhere, takes the form: “I have a list of identifiers (X); I want to relate them to a second set of identifiers (Y)”. HGNC gene symbols to Ensembl Gene IDs, for example.

When this occurs I have been known to tweet “the answer is BioMart” (there are often other solutions too) and I’ve written a couple of blog posts about the R package biomaRt in the past. However, I’ve realised that we need to take a step back and ask some basic questions that new users might have. How do I find what marts and datasets are available? How do I know what attributes and filters to use? How do I specify different genome build versions?
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Exploring the NCBI taxonomy database using Entrez Direct

I’ve been meaning to write about Entrez Direct, henceforth called edirect, for some time. This tweet provided me with an excuse:

This post is not strictly the answer to that question. Instead we’ll ask: which parent IDs of records for insects in the NCBI Taxonomy database have the most species IDs?
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Configuring the R BatchJobs package for Torque batch queues

I was asked recently to look at some R code which performs “embarrassingly parallel” computations (the same function, multiple times, different parameters) and see whether I could modify it to run on one of our high-performance computing clusters. The machine has 63 virtual compute nodes and uses the TORQUE batch queue system to allocate nodes to compute jobs.

First stop: the CRAN Task View High-Performance and Parallel Computing with R. Two promising packages there: BatchJobs and BatchExperiments. Their documentation is quite extensive with useful examples, but I found it a little disjointed and confusing. What I wanted was a simple, step-by-step guide to setting up for a first-time user. So here is my attempt. As always, it’s for “Linux-like” systems.
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PMRetract: PubMed retraction reporting rewritten as an interactive RMarkdown document

Back in 2010, I wrote a web application called PMRetract to monitor retraction notices in the PubMed database. It was written primarily as a way for me to explore some technologies: the Ruby web framework Sinatra, MongoDB (hosted at MongoHQ, now Compose) and Heroku, where the app was hosted.

I automated the update process using Rake and the whole thing ran pretty smoothly, in a “set and forget” kind of way for four years or so. However, the first era of PMRetract is over. Heroku have shut down git pushes to their “Bamboo Stack” – which runs applications using Ruby version 1.8.7 – and will shut down the stack on June 16 2015. Currently, I don’t have the time either to update my code for a newer Ruby version or to figure out the (frankly, near-unintelligible) instructions for migration to the newer Cedar stack.

So I figured now was a good time to learn some new skills, deal with a few issues and relaunch PMRetract as something easier to maintain and more portable. Here it is. As all the code is “out there” for viewing, I’ll just add few notes here regarding this latest incarnation.
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From PMID to BibTeX via BioRuby

Chris writes:

The blog post in question concerns conversion of PubMed PMIDs to BibTeX citations. However, a few things have changed since 2010.

Here’s what currently works.

Make prettier documents by reusing chunks in RMarkdown

No revelations here, just a little R tip for generating more readable documents.

Screenshot-RStudio.png

Original with lots of code at the top

There are times when I want to show code in a document, but I don’t want it to be the first thing that people see. What I want to see first is the output from that code. In this silly example, I want the reader to focus their attention on the result of myFunction(), which is 49.
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Bioinformatics journals: time from submission to acceptance, revisited

Before we start: yes, we’ve been here before. There was the Biostars question “Calculating Time From Submission To Publication / Degree Of Burden In Submitting A Paper.” That gave rise to Pierre’s excellent blog post and code + data on Figshare.

So why are we here again? 1. It’s been a couple of years. 2. This is the R (+ Ruby) version. 3. It’s always worth highlighting how the poor state of publicly-available data prevents us from doing what we’d like to do. In this case the interesting question “which bioinformatics journal should I submit to for rapid publication?” becomes “here’s an incomplete analysis using questionable data regarding publication dates.”

Let’s get it out of the way then.
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When life gives you coloured cells, make categories

Let’s start by making one thing clear. Using coloured cells in Excel to encode different categories of data is wrong. Next time colleagues explain excitedly how “green equals normal and red = tumour”, you must explain that (1) they have sinned and (2) what they meant to do was add a column containing the words “normal” and “tumour”.

I almost hesitate to write this post but…we have to deal with the world as it is, not as we would like it to be. So in the interests of just getting the job done: here’s one way to deal with coloured cells in Excel, should someone send them your way.
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Converting a spreadsheet of SMILES: my first OSM contribution

I’ve long admired the work of the Open Source Malaria Project. Unfortunately time and “day job” constraints prevent me from being as involved as I’d like.

So: I was happy to make a small contribution recently in response to this request for help:

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