Levenberg-Marquardt compromise

The Levenberg-Marquardt Method described in this section represents a compromise between the Gauss-Newton Method described in Section 19.4.1 and the Method of Steepest Descent described in Section 19.4.2. The Method of Steepest Descent is used far from the converged value, moving smoothly to the Gauss-Newton Method as the solution is approached. 

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