Parameter restrictions for Archimedean copulas
tnagler opened this issue · 2 comments
tnagler commented
Most functions for Archimedean copulas run into numerical problems when the absolute value of Kendall's tau is close to 1. The critical value varies between families and functions. We should:
- find critical values for each family
- prevent selection algorithms from selecting a family when the corresponding critical value is exceeded
- throw warnings or errors when infeasible parameter values were specified manually.
ulf85 commented
Concerning your second point: Bound for the BB copulas are already implemented. If a parameter value exceeds a certain value the selection algorithm switch to the boundery case, e.g. the Joe copula for some BB copulas.
For the first point we should have a look at our old stuff if we have already some bounds for some of the copulas.