Variogram

A semivariogram (short: variogram ) represents the spatial relationship of a point ( regionalized variable) to neighboring points dar. These are in various stages of removal ( " lag" ) point pairs formed. The squared differences of the pairs are then summed and divided by the amount of points (see variance). This results in the semi- variance, which is represented in a two-dimensional graph as a function of distance to the reference point.

Spherical variograms, - - exponential variograms, - linear variograms and - Gaussian variograms: Ideally, basic shapes that can be described by mathematical functions (theoretical variograms ) result.

Usually runs (exception: linear variogram ) semivariogram to a limit ( sill ). The distance between the first value (x = 0 ) and the point at which the y-values ​​reach the " sill " is called the " range". If y = f ( x) at x = 0 is greater than 0, then one speaks at y from the " nugget " - a measure of the noise.

Semivariograms have applications in kriging.