GS⁺ Variance Cloud Analysis

A variance cloud is a graph of the variances associated with individual pairs of points in an autocorrelation analysis. It is most useful for discovering outliers that can skew the average semivariance value for a lag class. By placing the mouse on top of individual points you can determine which pairs of points in the data set are suspect.

Variance clouds are specific to both direction (isotropic or a specific anisotropic direction) and to a particular lag class. In the example below the cloud is specific to the 7th lag class of the isotropic variogram, as noted in the graph title, and the mouse is on top of the pair made up of data records 4 and 96, which are separated by 52.77 distance units.  The List Values command lists numeric values for the cloud pairs in a separate Variance Cloud Listing window.  When the program is running you can click on a graphed point and be given the option of removing one of the records from the analysis, as explained below.

Variance Cloud analysis is initiated by clicking on a semivariance point on a variogram in either the Autocorrelation Analysis window or the Variogram window.