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Matrix Coherence and the Nystrom Method
Proceedings of the 26th Conference on Uncertainty in Artificial Intelligence, PMLR R8:579-586, 2010.
Abstract
The Nystr\"{}om method is an efficient technique used to speed up large-scale learning applications by generating low-rank approximations. Crucial to the performance of this technique is the assumption that a matrix can be well approximated by working exclusively with a subset of its columns. In this work we relate this assumption to the concept of matrix coherence, connecting coherence to the performance of the Nystr\"{}om method. Making use of related work in the compressed sensing and the matrix completion literature, we derive novel coherence-based bounds for the Nystr\"{}om method in the low-rank setting. We then present empirical results that corroborate these theoretical bounds. Finally, we present more general empirical results for the full-rank setting that convincingly demonstrate the ability of matrix coherence to measure the degree to which information can be extracted from a subset of columns.