Building Machine Learning Systems with Python - Third Edition

Features and feature engineering

One interesting aspect of these features is that the compactness feature is not actually a new measurement, but a function of the previous two features: area and perimeter. It is often very useful to derive new combined features. Trying to create new features is generally called feature engineering. It is sometimes seen as less glamorous than algorithms, but it often matters more for performance (a simple algorithm on well-chosen features will perform better than a fancy algorithm on not-so-good features).

In this case, the original researchers computed the compactness, which is a typical feature for shapes. It is also sometimes called roundness. This feature will have the same value for two kernels, one of ...