My city Coventry

Okay so a few weeks ago at work a colleague asked me where I was from in the UK, and I replied “Oh, it’s a small little town, you’ve probably never heard of it, Coventry. It’s close to Birmingham”. This is a natural response for me given that I lived in the US for a…

Galaxy clusters across cosmic time

I attended this conference in Aix-en-Provence this week. I gave a talk on my hierarchical analysis of galaxy clusters and there was a great turn out from the cluster community but lots of cluster environmentalists! Anyway some of the most interesting talks I found were: Michael Gregg from UC Davis, gave a really nice talk…

On Relative entropy

Relative entropy is a really cool tool that which haven’t heard of before you are in for a treat! Also known as Kullback-Leibler divergence, it is the measure of the distance between 2 probability distributions [e.g. p(x) and q(x) ]  on a random variable X. It is defined as: Where H(P,Q) is the cross entropy…

Multivariate Gaussian Mixture Model done properly

Michael Betancourt recently wrote a nice case study describing the problems often encountered with gaussian mixture models, specifically the estimation of parameters of a mixture model and identifiability i.e. the problem with labelling mixtures (http://mc-stan.org/documentation/case-studies/identifying_mixture_models.html). Also there has been suggestions that GMM’s can’t be easily done in Stan. I’ve found various examples online of simple…

Best space themed christmas ideas…

Its almost christmas and time to think about christmas presents. Below i list my top 10 christmas presents for the astronomy/space obsessed! 10. Time Travelling Toby and the Apollo moon landing by Graham Jones Graham Jones’ exciting take on the Apollo moon landings, this beautifully illustrated book is the perfect gift for those young kids (1-10)…