As the gene expression data owns the characteristics of nonlinear and high noise, normal Euclidean distance can not represent the similarity measurement between genes.

Introduces color feature extraction and matching algorithms in content-based image retrieval, such as weighted Euclidean-distance, weighted centre distance, histogram intersection algorithm, etc.

This paper briefly introduces two classes of methods for molecular 3D structure comparison, one is based on Euclidean distances, and another is based on relativity of properties.