In Signal Processing a Filter is a device or process that removes or suppresses some unwanted components or features from a signal. Most often this means removing some frequencies or frequency bands; however, many other targets for filtering exist. The objective of this paper is to connect some filters using developed mathematical concepts, which provides a good picturization of filters in Signal Processing and consequently facilitates the determination of the output of the filter for a given input. We also discuss some special cases of filtering and try to picturize those filters. We also try to extend this idea of filtering to directed graphs.