A procedure for revealing trends in scatter diagrams by determining typical values based on observation of successive small intervals of the explanatory variable. Simple examples are provided by the running mean and running median. For a data set, y₁, y₂, y₃,…, ordered by the corresponding values of the explanatory variable, the three-point running means are given bywhile, denoting the median of y_i−1, y_i, and y_i+1 by M(y_i), for i > 1, the three-point running median values would be M(y₂), M(y₃), M(y₄),…. These ideas can be extended by calculating, for example, M(M(y_j)). More sophisticated alternatives are kernel methods, loess, and the use of splines. See also generalized additive model.