Theta Criteria are based on operator's theory and matrices decompositions. The main idea is to evaluate differences between sets of operators' eigenvalues & eigenvectors or eigenfunctions. Theta Criteria will lead to more efficient analysis, optimization and prognosis of multivariate systems and applications. Theta Criteria can be used for data set mining and image processing. The book is designed as a complementary tool for applied mathematics methods. More information at: www.ThetaCriteria.com Keywords: Block matrices, Canonical analysis, Condition, Determinant, Eigenfunctions, Eigenpair,...