elementary_score: Elementary Scoring Function for Expectiles and Quantiles
Description
Weighted average of the elementary scoring function for expectiles resp. quantiles at level alpha with parameter theta, see reference below.
Every choice of theta gives a scoring function consistent for the expectile resp. quantile at level alpha.
Note that the expectile at level alpha = 0.5 is the expectation (mean).
The smaller the score, the better.
Ehm, W., Gneiting, T., Jordan, A. and Krüger, F. (2016), Of quantiles and expectiles: consistent scoring functions, Choquet representations and forecast rankings. J. R. Stat. Soc. B, 78: 505-562, <doi.org/10.1111/rssb.12154>.