by **Didier Renard** » Sun Mar 18, 2018 9:57 pm

When changing the scale of the variable of interest (say dividing it by 1000), the variance (and hence the units along the variogram axis) are divided by 1,000,000.

Then model.auto procedure must follow the same scale change.

If we consider 'diff' the gap between the experimental variogram and the model; during the iterations, if 'diff' becomes smaller than 'tolstop' the iterations stop. It is considered that the convergence has been reached.

Unfortunately this parameter 'tolstop' is not scaled as a function of the sill or the variance of the data. Then the user must adapt the value of 'tolstop' to the order of magnitude of the variance of the target variable.

In your case, due to very small variability of the data, the value of 'diff' was considered as smaller than 'tolstop' after a very limited number of iterations (say 2). The program stops while the fit is not correct.

The workaround is simply to reduce the value of 'tolcode'. Put it to 1.e-10 for example.