Why machine learning?

The purpose of classification is to extract knowledge from historical data. For instance, a classifier can be built to identify a disease from a set of symptoms. The scientist collects information regarding the body temperature (continuous variable), congestion (discrete variables HIGH, MEDIUM, and LOW), and the actual diagnostic (flu). This dataset is used to create a model such as IF temperature > 102 AND congestion = HIGH THEN patient has the flu (probability 0.72), which doctors can use in their diagnostic.

Once the model is extracted and validated against the past data, it can be used to draw inference from the future data. A doctor collects symptoms from a patient, such as body temperature and nasal congestion, and anticipates the state of his/her health.

Some global optimization problems are intractable using traditional linear and non-linear optimization methods. Machine learning techniques improve the chances that the optimization method converges toward a solution (intelligent search). You can imagine that fighting the spread of a new virus requires optimizing a process that may evolve over time as more symptoms and cases are uncovered.

Regression is a classification technique that is particularly suitable for a continuous model. Linear (least square), polynomial, and logistic regressions are among the most commonly used techniques to fit a parametric model, or function, y= f (xj), to a dataset. Regression is sometimes regarded as a specialized case of classification for which the output variables are continuous instead of categorical.