After all, the moment of activation of a relevant regressor then equals formula 144. For instance, the third regressor could be the square of the second regressor. This sum is thus equal to the constant term's regressor, the first vector of ones. OLS can handle non-linear relationships by introducing the regressor HEIGHT. In this case, the coefficient on the regressor of interest is given by formula 14. This generated regressor method is also applicable to unobserved instrumental variables. The regressor matrix and formula 146 the vector of response variables.