Research Talk: Anomaly Detection Using Expert Feedback

November 19, 2009
Halligan 111B
Speaker: Saeed Majidi, Tufts University


Anomaly or outlier detection seeks to detect patterns in a given data set that do not conform to expected behavior. For the majority of both supervised and unsupervised anomaly detection methods, points are ranked with respect to an anomaly score that is based on a distance measure defined over the features describing each instance in the dataset. The domain expert can then examine this ranked list of anomalies. A potential flaw in this approach is that existing methods weight all features equally in computing an anomaly score for each instance. However, the expert might consider being anomalous in some features to be far more interesting than being anomalous in all of the features. In this talk we present a method that takes feedback from the expert in order to determine a set of weights on the features for the distance metric. Specifically, at each iteration, the expert examines the top k points in the ranked list, and indicates whether or not they are “interesting” anomalies. From this feedback our method recalculates the weights for the features with the goal of ensuring that more anomalous points appear higher in the ranking on the next iteration. Our research is motivated by the problem of finding anomalous objects in astronomy photometric time series and we show preliminary results of our method on this dataset.