Here's an interesting probabilistic way to sample up to the median: http://blog.aggregateknowledge.com/2013/09/16/sketch-of-the-day-frugal-streaming/ http://bl

Here's an interesting probabilistic way to sample up to the median: http://blog.aggregateknowledge.com/2013/09/16/sketch-of-the-day-frugal-streaming/ http://blog.aggregateknowledge.com/2013/09/16/sketch-of-the-...