Least Squares Regression

Residuals

By plotting the residuals (deviations from the regression line), one can make sure that the data does not have unlinearities.

plot of residuals

If the residuals are not more or less randomly distributed around zero but shows some kind of systematic curvature, it means that the data contains unmodeled information. One should then consider other empirical models or use a soft-modelling technique like PCR or PLSR.



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