Generalized regression (GRNN) and probabilistic (PNN) networks are variants of the radial basis function (RBF) network. Unlike the standard RBF, the weights of theses networks can be calculated analytically. In this case, the number of cluster centers is by definition equal to the number of exemplars, and they are all set to the same variance. Use this type of RBF only when the number of exemplars is so small (<100) or so dispersed that clustering is ill-defined.
