1. A method comprising: receiving at least one stream of data; and creating data blocks from the at least one stream of data, each data block comprising: a pair of timestamps indicating a sampling start time and a sampling end time; a number of data samples spanned by the data block; a SUM(X) statistic computed for the data samples spanned by the data block; a SUM(XX) statistic computed for the data samples spanned by the data block; and a SUM(XY) statistic computed for the data samples spanned by the data block.