[MRG] FIX: Output NaN columns for CompCor on failure

[effigies]

Closes #1433.

Changes proposed in this pull request

• Use failure_mode parameter added ENH: Add NaN failure mode to CompCor interfaces nipy/nipype#2819 to produce columns of NaNs when SVD fails to converge.

Documentation that should be reviewed

[oesteban]

Should we add a warning to the reports when the column is all NaNs?

[effigies]

I think that's probably a good idea, but haven't gotten around to it. I think a small warning box just below the BOLD masks figure would make the most sense.

Perhaps text like:

Warning: [at]CompCor components could not be estimated, due to a linear algebra error.
While not definitive, this may be an indication of a poor mask. Please inspect the (magenta|blue)
contours above to ensure that they are located in the white matter/CSF.

[oesteban]

Ref nipreps/niworkflows#268

[effigies]

@oesteban If you could review the logic of the new patched interfaces, that's the most likely place to need fixes. I added a snippet that will only show up as a comment so we can verify this in the CircleCI artifacts.

[oesteban]

Left some comments, but looking very good in general.

I wonder whether after 10 failures we should call it an error (i.e. always raise in that case)

[oesteban]

Should we add a strict check here that mask.sum() > 1 and raise if not?: https://github.com/nipy/nipype/blob/fbed1f3c432e80b1e199f93d17e4d8f1da232897/nipype/algorithms/confounds.py#L1155

[effigies]

We could do that, but why raise an error instead of issue a warning? The whole point of this is not to crash. People who care about CompCor can worry about why, but if they don't, the masks don't matter at all.

[effigies]

I wonder whether after 10 failures we should call it an error (i.e. always raise in that case)

We already do that. The point is to give it a few chances to work and gracefully fail.

[effigies]

Needs to be fixed before merge, but proof of concept works, so merging nipy/nipype#2819 and can make a final round of cleanups in one go and check the CI output.