Hi Maxi,
Commits 26ef3a3b5032, 90875aa7e993, 41ddbdc23746 and this one (e2b668b5985a) are about the issues we talked about yesterday.
You can now define LinearFunctions by providing two points (either as two std::pair's containing the coordinates or as x1, y1, x2, y2). These can be changed by setter methods.

I thought about the issue with that function that changes depending on the number of samples. I implemented a StepFunction for that. That function represents a step-function from 0 to 1, where the step itself is not a jump but a slope from 0 to 1. You provide the coefficient of the slope in the constructor and can change it via a setter method (you can also change it with setRightLimit, which sets the point where the function shall switch to 1).

Consider the following:

StepFunction<float, float> sf(0.5);

This would create a function that evalutes to 0 for values <= 0, to 1 for values >= 2 and to 0.5*value for all other values.
Then, you could do:

sf.setCoefficient(0.25)

or

sf.setRightLimit(4)

To move the right limit to 4 (0 for values <= 0, 1 for values >= 4, 0.25*value else).
This should be exactly what you need for now.