Trying to follow the calculations in the linearExtrapolator class:
Especially this line :
result[i] = -result[i] * (xValue - lastXValue) / eps;
which calculates the parametersensitivities of an xvalue on the extrpolated right part. this line of code applies for nodes except the last one.
The second term on the right I interprete as the derivative of the extrapolation function with respect to node i. Is that correct? Why is parametersensitivity to (lastXValue - eps) and not lastXvalue used (result)? Hopefully some quick answers otherwise maybe a reference to read more of this.