Add ordinal regression algorithms and/or problem

[johann-petrak]

not sure about this, needs more thinking! This is about predicting per-instance ordinal values where we only know the partial ordering of targets but where the target value is otherwise not on an interval or ratio scale.

[johann-petrak]

Copied over from redundant #47 :
Have a look how difficult it would be to add ordinal regression. This would be useful for targets like ordered degrees of sentiment, reviews etc.
There is a mention of a Python implementation here: http://fa.bianp.net/blog/2013/logistic-ordinal-regression/ (see also http://pythonhosted.org/mord/) and there are some R packages for that.
Also, proper coding and definition of the cost function with NN may work?