This makes the testing and therefore the program faster. This function returns the covariance associated with a variogram model c that is specified by a nugget effect and possibly four different c nested varigoram structures. A unique value of PMX is c used for all nested structures which use the c power model. Multiplicative factor of each nested structure. Requires the upper triangular left hand side matrix.
Pivots are on the diagonal.
Does not search for max. Several right hand side matrices possible.