This paper examines properties and interrelations of several concepts of generalized concavity. It shows that the class of functions that are both 'generalized concave' and 'generalized convex' is ...

, Enno Mammen, Byeong U. Park, , On Estimation of Monotone and Concave Frontier Functions, Journal of the American Statistical Association, Vol. 94, No. 445 (Mar ...

We compare and contrast concave and convex lenses by drawing ray diagrams.