1. The problem statement, all variables and given/known data I have two different experimental curves, and I would like to measure how closely a straight line fits each data, and which curve is more crooked. In statistics how can I measure this "linearity"? By the way this is about stepper motor step linearity (ideally it has to be a straight line i.e. homogeneous step sizes). I am comparing the two plots made for two different speeds: 2. Relevant equations 3. The attempt at a solution I'm new to stats and I'm not sure what method to use. I'm very confused because some websites say I have to calculate the ##R^2## value, while others say I need a some kind of regression line. So, if the linearity could somehow be determined from the equation of regression line, what kind of regression do I need to use (linear or quadratic, cubic, etc)? And how exactly do I determine linearity from that equation? Any explanation is greatly appreciated. P.S. I am using Matlab.