Self-Organizing Maps

Self-organizing maps are an old idea (first published in 1989) and take strong inspiration from some empirical neurophysiological observations from that time. The original paper "Self-Organizing Semantic Maps" by Ritter and Kohonen (pdf) has a nice discussion that took me back to some questions I was looking at in another life as a neurophysiologist. The …

Advertisements

Balancing training examples in classes

This one was a little non-intuitive for me. I had a combination of neural and behavioral data from an experiment I'm running. The behavioral data has two categories: Correct and Incorrect (depending on whether the subject performed the task correctly on that particular trial). The neural data takes the form of a feature vector. So …

Support Vector Machines and dimensionality

When I was introduced to support vector machines I initially thought: this is great, the method takes care of irrelevant dimensions. My intuition was that since the algorithm tilts hyperplanes to cut the space, adding irrelevant dimensions does not matter at all, since the hyperplane would just lie parallel to the irrelevant dimensions. Practically speaking, …