[pymvpa] every permutation returning the same value

[Nick Oosterhof]

On Aug 31, 2014, at 4:24 PM, Ben Acland <benacland at gmail.com> wrote:

> Can anyone see a mistake in the following code that would cause all of my permutation tests to return the same mean error value? 
> 
> # cross-validated linear svm with permutation testing (leave out 1 from each sub group)
> rep = mp.Repeater(count=PERM_COUNT)

[...]

> distr_est = mp.MCNullDist(rep,
>                          tail='left',
>                          measure=null_cv,
>                          enable_ca=['dist_samples'])

[...]

> ... and at the end of all of this, cvmcc.null_dist.ca.dist_samples contains PERM_COUNT repetitions of a single value.

You are feeding your Repeater as the permutator argument. It would seem that the MCNullDist has no access to unpermuted datasets.