L-curve

L-curve is a visualization method used in the field of regularization in numerical analysis and mathematical optimization.^[1] It represents a logarithmic plot where the norm of a regularized solution is plotted against the norm of the corresponding residual norm. It is useful for picking an appropriate regularization parameter for the given data.^[2]

This method can be applied on methods of regularization of least-square problems, such as Tikhonov regularization and the Truncated SVD,^[2] and iterative methods of solving ill-posed inverse problems, such as the Landweber algorithm, Modified Richardson iteration and Conjugate gradient method.