I've been working a little bit more with the `namedtuples` on the ordination stuff. If you don't have all the fields always, I can see that subclassing is more useful, so you don't need to specify `None` for those fields that you don't have data. Take a look to the [`OrdinationResults` class](https://github.com/biocore/scikit-bio/blob/master/skbio/maths/stats/ordination/base.py#L15).