1. An analog system for sparsely approximating a signal comprising: a matching system for calculating and outputting matching signals representative of how well-matched said signal is to a plurality of dictionary elements; and a plurality of nodes, each node receiving one of said matching signals from said matching system, wherein each node comprises: a source of an internal state signal; and a thresholding element; wherein said internal state signal in each node is calculated as a function of said matching signal received at said node and weighted outputs of all other nodes.