This command defines one of the criteria used for automatic parameter selection. It examines the ratio between the apparent conditional standard deviation sigma* and the joint standard deviation sigma as a measure of overall parameter correlation (since the calculation is performed far from the minimum, the standard deviations cannot be interpreted as actual estimation uncertainties):
Those parameters with a ratio larger than |rcorr|, i.e., the most independent parameters, are selected. Strongly correlated parameters are (temporarily) excluded from the optimization process. If a negative value is given for rcorr, the selection criterion is relaxed with each iteration k, and reaches zero for the last iteration max_iter, i.e., all parameters are selected for the final step.
The choice for rcorr depends on the number of parameters n specified in block
>>> SELECT parameter automatically every
>>>> : 3 ITERATIONS
>>>> based on the CORRELATION criterion with rcorr : -0.10