Rank association is a fundamental tool to express dependence for ordinal data. Measures of rank correlation have been developed in several contexts for more than a century and we were able to cite more than thirty of these coefficients, from simple ones to relatively complicated definitions...

In a less widely known contribution, Béla Martos (1966, Hungarian Academy of Sciences) introduced a generalized notion of concavity that is closely related to what is nowadays known as r-concavity in the operations research literature, and that is identical to what is nowadays known as...

We define a standard optimization problem with quadratic objective function and provide a rigorous visual proof for its solution without using calculus. We then show that such standard problem is a building block for several economic models related to microeconomics, game theory and pricing...

For classification problems with ordinal attributes very often the class attribute should increase with each or some of the explaining attributes. These are called classification problems with monotonicity constraints. Classical decision tree algorithms such as CART or C4.5 generally do not...