The default scaling variance returns always 1.

Marks a class as containing one or more static functions that create a fit function class.

Marks a static function to return a new instance of a class.

Represents the interface to a fitting function.

Interface to how to scale the differences between real quantities (dependent variables) and fitted values.

This is a variance which scales linearly with the measured value. Useful for functions with a broad range of y-values. Make sure that no y-value is zero.