John Lees' blog

Pathogens, informatics and modelling at EMBL-EBI

When to use log scales

log scales seem to have caused a lot of debate recently. When should we use them? I think there are two reasons: Your data is exponentially distributed. You want to transform your data to make certain regions easier to see. Exponentially distributed data The first is a bit of a tautology. For independent variables (usually the x-axis) it’s easy. Perhaps you have collected data at points 1, 2, 4, 8, 16 etc.

Easy debugging of C/C++/CUDA python extensions

Writing an extension called by python (in C, C++ or CUDA)? Not working? Typical. When doing the same from R it’s pretty easy to debug, just run with R -d <debugger name> e.g. R -d valgrind or R -d gdb you get into the debugger, continue, then run interactively as usual. (For a more complex example using both at once see this blog post). Doing this from python seems trickier to me.

p-value < 2.2e-16

A claim: 2.2e-16 is the most popular p-value in research papers, even more popular than 0.05 (or if you’re being cynical 0.049). Why? 2.2e-16 happens to be the epsilon of a double-precision float (i.e. a decimal number stored using 64 bits). Roughly, this means that if you try to calculate 1 - epsilon, with anything smaller than epsilon, the answer will be 1. In R, you can calculate this by running the following code (+2 due to convention):

Honey Roast Parsnips (frozen), Iceland

A review of ‘Honey Roast Parsnips’ - available from Iceland ¬£1.75, 750g This weekend I wanted to buy some parsnips to roast, but they were absent from the produce section (except in a pack coming with four unwanted carrots, and one considerably more unwanted turnip). However, as I was shopping at Iceland, there was a handy pre-prepared frozen alternative: These cost roughly double the amount of buying raw parsnips. I’d estimate there are around four large portions in this bag, you can probably get double that if you’re using a small amount.

Screamadelica, Primal Scream

Why is it only in 2021 that I am listening to Primal Scream’s Screamadelica for the first time? A lot of critically acclaimed music from the 1980s maintains a pop appeal that means it still gets radio play, is featured in club nights, and is heavily promoted in my Youtube home. However, perhaps the post-rock, trip-hop and grunge of the early 1990s doesn’t have the same enduring commercial appeal. Whatever the reason, I’ve been missing out.

Porting a bioinformatics tool to the web using WebAssembly, React and javascript

We recently released a beta version of PopPUNK-web (https://web.poppunk.net). This is a WebAssembly (WASM) version of pp-sketchlib which sketches an user-input genome assembly in the browser; transmits this sketch as a JSON to a server running PopPUNK using gunicorn and flask; runs query assignment against a large database of genomes from the GPS project; returns a JSON containing strain assignment, a tree and network; these are then displayed using a react app.