Non-parametric cluster correction single subj

Dear Alfonso,

I think I ran into a bug, or at least an undocumented limitation.

I would like to use a non-parametric cluster correction for a single subject against a control group.

The calculation of the permutation test runs fine, but after the calculation, I get a threshold equivalent to k > 1 (thus cluster uncorrected, equivalent to cluster-size = 0) for any non-parametric threshold type I choose, and any threshold value!

Clearly this means that the permutation test could not work correctly in this instance. However I can make it work with all my other studies involving group A vs group B, or session 1 vs session 2, so I guess the limitation here is because one group contains only a single subject.

Is it really impossible to do a permutation test with only a single subject? If that's the case, maybe adding a warning window would be useful? (to avoid experimenters using the non-parametric test when in fact it does not correct anything).

Thank you very much for clarifying this issue and helping!

Warm regards,
Stephen Larroque