A Streaming Algorithm for the Convex Hull.

We study the 2-center problem with outliers in high-dimensional data streams. Given a stream of points in arbitrary d dimensions, the goal is to find two congruent balls of minimum radius covering all but at most z points. We present a ( 1.8 + ε ) -approximation streaming algorithm, improving over the previous ( 4 + ε ) -approximation algorithm available for the problem. The space complexity and update time of our algorithm are poly ( d , z , 1 / ε ) , independent of the size of the stream.