mages' blog

Last Tuesday we got together for the 4th Bayesian Mixer Meetup. Product Madness kindly hosted us at their offices in Euston Square. About 50 Bayesians came along; the biggest turn up thus far, including developers of PyMC3 (Peadar Coyle) and Stan (Michael Betancourt).

The agenda had two feature talks by Dominic Steinitz and Volodymyr Kazantsev and a lightning talk by Jon Sedar.

Dominic Steinitz: Hamiltonian and Sequential MC samplers to model ecosystems

Dominic shared with us his experience of using Hamiltonian and Sequential Monte Carlo samplers to model ecosystems.

Volodymyr Kazantsev: Bayesian Model Averaging

Finding the 'best' model was Volodymyr's challenge. He tried various R packages (BMA, BMS and BAS) for Bayesian model averaging, with various degrees of success.

Jon Sedar: Easier Plate Notation in Python using Daft

Finally, Jon gave a brief overview on Daft, a nifty Python package for creating graphs, or plate notation.

Next meeting

The next Bayesian Mixer Meetup meeting is already scheduled for 21 October. We will be back at Cass Business School, with two talks:

• Darren Wilkinson: Hierarchical Bayesian Modelling of Growth Curves inc Stochastic Processes
• Peadar Coyle: Advanced PyMC3

Have I missed unknown pleasures in Python by focusing on R?

A comment on my blog post of last week suggested just that. Reason enough to explore Python a little. Learning another computer language is like learning another human language - it takes time. Often it is helpful to start by translating from the new language back into the old one.

I found a Python script by Ludwig Schwardt that creates a plot like this:


It is only a small Python script, but it illustrated how to:

• load packages
• use conditional statements
• add comments
• write functions
• deal with arrays
• write loops
• create plots
• save output into a PDF file

Here is my translation into R, which actually generated the plot above.

R code

Session Info

R version 3.1.2 (2014-10-31)
Platform: x86_64-apple-darwin13.4.0 (64-bit)

locale:
[1] en_GB.UTF-8/en_GB.UTF-8/en_GB.UTF-8/C/en_GB.UTF-8/en_GB.UTF-8

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods  
[7] base     

other attached packages:
[1] signal_0.7-4 e1071_1.6-4 

loaded via a namespace (and not attached):
[1] class_7.3-11 MASS_7.3-35  tools_3.1.2