Classifier (mathematics)

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In mathematics, a classifier is a mapping from a (discrete or continuous) feature space X to a discrete set of labels Y.

Classifiers have practical applications in many branches of science and society. Built using a variety of mathematical techniques, classifiers viewed from afar can be seen as decision systems which accept values of some features or characteristics of a situation as input and produce as an output a discrete label related to the input values.

An example might be a classifier which accepts a persons salary details, age, marital status, home address and credit history and classifies the person as acceptable/unacceptable to receive a new credit card or loan.

The application of classifiers is wideranging and often unseen. They find use in medicine (drug trial analysis, MRI data analysis), finance (share analysis, index prediction), mobile phones (signal decoding, error correction), computer vision (face recognition, target tracking), voice recognition, datamining (supermarket purchasing analysis, retail customer analysis) and uncountable other areas.

Classifiers may either be fixed classifiers or learning classifiers, and learning classifiers may in turn be divided into supervised and unsupervised learning classifiers.

For a list of classifier applications and classifier technologies, please see statistical classification.