Line fitting is the process of constructing a straight line that has the best fit to a series of data points.

Several methods exist, considering:

• Vertical distance: Simple linear regression
• Resistance to outliers: Robust simple linear regression
• Perpendicular distance: Orthogonal regression (this is not scale-invariant i.e. changing the measurement units leads to a different line.)
• Weighted geometric distance: Deming regression
• Scale invariant approach: Major axis regression This allows for measurement error in both variables, and gives an equivalent equation if the measurement units are altered.