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CRANFIELD UNIVERSITY Eleni Anthippi Chatzimichali ...

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c)<br />

Figure 2-8 Comparison of the optimisation of the hyperparameters of RBF SVMs via<br />

bootstrapping, 10-fold cross-validation and LOOCV respectively<br />

The grid plots demonstrate the dependence of the overall prediction error on the RBF hyperparameters<br />

C and for different optimisation (validation) techniques. The FTIR data were used for demonstrative<br />

purposes. The total number of hyperparameter combinations forms a grid of 6561 points. A colour<br />

scheme is used to emphasise the divergence in performance. Grid points with dark blue colour are<br />

considered optimal since they correspond to robust combinations of hyperparameters with low error;<br />

on the contrary, areas with dark red colour result in high error (rates) and hence are considered<br />

unacceptable.<br />

55

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