Devices for selecting or excluding data from a data stream or data set. These devices may be physical (for example to tune an electrical circuit to a particular frequency) or a mathematical algorithm. Mathematical filters take many forms, some of which are used in oilfield data analysis and interpretation. Examples include statistical techniques, geostatistical techniques, clustering, conditional algorithm, etc. A simple example of a conditional algorithm might include using a caliper to determine whether a borehole was rugose, thus requiring special log interpretation through the rugose interval.