Monitor: Adding "RER" and "RPD" statistics

I continue developing the Monitor function in R. The idea is to get statistics which help me to understand the performance of my model.

Of course the validation set must be free of outliers (X or Y).

I add this time two new statistics: RER and RPD.

These statistics must be treated with caution, because depends of the range, standard deviation and number of samples for the validation set.

See the new video for the calculation of these statistics in "R":
 Monitor: Adding "RER" and "RPD" statistics