Schematic representation of some general model classes. (a) Typical perceptron model, (b) single-type basis function models, (c) multitype basis function models. The solid lines correspond to parameters that must be estimated. Dashed lines indicate absence of parameters. Therefore (a) is nonlinear in the parameters whilst (b) and (c) are linear in the parameters. Usually depends on some parameters. When this is the case, such parameters are chosen beforehand. Figure reproduced from [77].
