regr.featureless: Featureless regression learner.
Description
A very basic baseline method which is useful for model comparisons (if you
don't beat this, you very likely have a problem).
Does not consider any features of the task and only uses the target feature
of the training data to make predictions.
Using observation weights is currently not supported. Methods “mean” and “median” always predict a constant value
for each new observation which corresponds to the observed mean or median of
the target feature in training data, respectively. The default method is “mean” which corresponds to the ZeroR algorithm
from WEKA, see https://weka.wikispaces.com/ZeroR.