Hi all. well, I'm geting problems when trying to calculate the absolute error of an average velocity. I've got a graphic of points generated by a sensor which scans an object position everey 0.05 seconds. concretely i need to calculate the average velocity between two points, at first two nearby points and then two further points. heretofore there is no inconvenient, but when i try on estimating the error by using partial derivates... I'm sure that something is wrong, because the further points give me a smaller error. How can I do to estimate ther error of the average Velocity expresed by (x2 - x1) / (t2 - t1)? thanks PD: excuse my english, but there's not good forums in my language.