In New York, you must be a registered Democrat or Republican to vote in the primary election; a portion of the 16 percent from that district might not know that. New Yorkers registered with a third party, such as the Green Party, Independence Party, Libertarian Party or Working Families Party, can't vote in the primary.
Collaborative filtering (CF) is a method used by some recommender systems. It consists of two senses, a narrow one and a more general one. In general, collaborative filtering is the process of filtering for information or patterns using techniques involving collaboration among multiple agents, viewpoints, data sources.
Introduction to DSP - filtering: frequency selective process. Filtering is a process of selecting, or suppressing, certain frequency components of a signal. A coffee filter allows small particles to pass while trapping the larger grains. A digital filter does a similar thing, but with more subtlety.