Measure to compare true observed response with predicted response in regression tasks.

## Arguments

- truth
(

`numeric()`

)

True (observed) values. Must have the same length as`response`

.- response
(

`numeric()`

)

Predicted response values. Must have the same length as`truth`

.- na_value
(

`numeric(1)`

)

Value that should be returned if the measure is not defined for the input (as described in the note). Default is`NaN`

.- ...
(

`any`

)

Additional arguments. Currently ignored.

## Details

The Relative Absolute Error is defined as $$ \frac{\sum_{i=1}^n \left| t_i - r_i \right|}{\sum_{i=1}^n \left| t_i - \bar{t} \right|}. $$ Can be interpreted as absolute error of the predictions relative to a naive model predicting the mean.

This measure is undefined for constant \(t\).