featuresvolume

Featuresvolume is a term used in data analysis to denote a summary of how much of the feature space is utilized by a dataset or representation. It is a scalar intended to reflect the spread or diversity of features after preprocessing. Because feature space is defined by the chosen features, featuresvolume depends on the feature set, scaling, and dimensionality.

Several definitions are used in practice. One common approach is the volume of the convex hull of the data points in the feature space, which captures the actual span of observed feature combinations but can be costly in high dimensions. A more tractable alternative is the product of per-feature ranges after normalization to a fixed interval, yielding a simple proxy for occupied volume. A third approach uses the generalized variance, defined as the determinant of the feature covariance matrix, describing the ellipsoidal volume of the data distribution around its centroid.

Applications include assessing feature diversity, comparing feature extraction pipelines, and monitoring changes during feature engineering or data augmentation. It can inform model choice or normalization decisions by indicating when a representation has expanded or contracted the accessible feature space.

Limitations include sensitivity to outliers, dependence on scaling and feature selection, and the curse of dimensionality in high-dimensional spaces. In practice, researchers often report more than one variant of featuresvolume.

See also: feature space, dimensionality, convex hull, generalized variance, covariance matrix, feature engineering.