Feb 04

## Use Enthought for scientific python

I’ve spent many hours attempting to install numpy and scipy from source on both Linux at work and Mac OS X at home. I could never get the big speedups possible from good numerical libraries like BLAS and ATLAS. Enthought’s one-click install python distribution turned out to be the perfect solution.

Jan 22

## Why probability contours for the multivariate Gaussian are elliptical

Every 2D Gaussian concentrates its mass at a particular point (a “bump”), with mass falling off steadily away from its peak.  If we plot regions that have the *same* height on the bump (the same density under the PDF), it turns out they have a particular form: an ellipse.  In this post, I’ll use math …

Nov 13

## Practical Bayesian Optimization with Spearmint

Recently, I’ve become interested in using Gaussian Processes for hyperparameter optimization. Coincidentally, there’s a great  NIPS 2012 paper by Jasper Snoek, Hugo Larochelle, and Ryan Adams about that very topic. Thankfully, not only is the paper insightful, but they also have Python source code available, called “spearmint” (I guess they chose the name so that …

Sep 30

## Review of STAN: off-the-shelf Hamiltonian MCMC

Recently, some folks at Andrew Gelman’s research lab have released a new and exciting inference package called STAN.  STAN is designed to do MCMC inference “off-the-shelf”, given just observed data and a BUGS-like definition of the probabilistic model.  I’ve played around with STAN in some detail, and my high-level review is summarized here Good: Installation …

Sep 01

## Using Voodoo to Estimate Handheld Camera Motion

I’m currently investigating fully automatic methods to determine the motion of a handheld cameras in unconstrained environments. Basically, if action recognition is going to work well in unconstrained videos, we need video representations that distinguish between motions that are “signal” (moving actors, moving objects) and motions that are irrelevant noise due to camera motion (panning, …

Aug 30

## Dense Trajectories for Action Recognition

Here, I take a qualitative look at one of the most successful video representations in use today: dense trajectories. You can find the original CVPR 2011 paper by Wang, Klaser, Schmid, and Liu here: Action Recognition by Dense Trajectories. I’m mostly interested in evaluating how well the provided code does at finding good trajectories for videos …

Aug 18

## Elliptical Slice Sampling for priors with non-zero mean

I’ve been playing around with elliptical slice sampling (ESS) lately.  This is a new MCMC technique developed by Iain Murray, Ryan Adams, and David MacKay. Here is the original AISTATS paper. The punchline is that this method allows exact joint sampling for vectors whose posterior distribution can be expressed using any Gaussian prior and any …

Aug 14

## ICML 2012 Highlights

After attending ICML 2012 in Edinburgh a month ago, I suppose a summary of my favorite papers and presentations is long overdue. Overall, Edinburgh provided a beautiful setting for the conference, and famously dreary Scotland weather even cooperated with a few days of sunshine.

Jul 12

## CVPR 2012 Highlights

In early June, I attended CVPR, a premier vision conference.  Luckily for me, the conference was right here in Providence just 20 minutes from Brown, so I didn’t have far to go. Definitely, one highlight was the lobster dinner, served to all 1000+ attendees.  After the jump, I’ll summarize some of my favorite research highlights. …

Jul 12

## Blog Basics

This sample post shows how to this site can include typeset mathematics and short code snippets. Typesetting is possible via the QuickLaTeX plugin. Code via the SyntaxHighlighter Evolved plugin.