Exercise 2 was to demonstrate by how much cinterp(X,Y,x) could be OFF track !
Most likely, you will never encounter such problem in Engineering projects.
Quadratic Holistic will be very useful in cases of few points looking very
linear, but in fact aren't. A spline tool worth to be available/working.

Jean

Spline l_p_c [ainterp, Holistic].sm (98,79 KiB) scaricato 1120 volta(e).