PsiKendallTau() returns a non-parametric correlation coefficient (based on the relative ordering or ranks) between two uncertain variables or functions, cell1 and cell2. This statistic can be used to determine how (if at all) the two uncertain variables or functions are correlated.
The Kendall Tau rank correlation coefficient measures the ordinal association between two uncertain variables or functions. It is a measure of rank correlation. This correlation coefficient is high when observations have a similar rank between the two variables, and low when observations have a dissimilar rank between the two variables.