As in the ANN analysis, the input and output data are normalized
into the [1 +1] range by Eq. (15). In the experiment, the
radial basis function (RBF) kernel with r2 bandwidth is used
because it tends to achieve better performance than other kernel
functions. No major variations occurred in the upper and lower
values of the [30–200] and [0.1–1.9] ranges of the C and r2 parameters
respectively, and the trainers with the lowest error rate
occurred in this range. In determining the kernel bandwidth, r2