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Variogram

In spatial statistics the theoretical variogram 2γ(x, y) is a function describing the degree of spatial dependence of a spatial random field or stochastic processZ(x).

As a concrete example from the field of gold mining, a variogram will give a measure of how much two samples taken from the mining area will vary in gold percentage depending on the distance between those samples. Samples taken far apart will vary more than samples taken close to each other.

Wiktionary

variogram

n. (context statistics English) A function of the spatial dependence of variance; a graph of this function