We will adopt the popular gaussian kernel, which presents less parameters
than other kernels (e.g. polynomial) [25]: K(x, x′) = exp(−γ||x − x′||2), γ > 0.
Under this setup, the SVM performance is affected by three parameters: γ, ε and
C (a trade-off between fitting the errors and the flatness of the mapping). To
−ε 0 +ε Fig.2. Example of a multilayer perceptron with 3 inputs, 2 hidden nodes and one
reduce the search space, the first two values will be set using the heuristics [4]:
C = 3 (for a standardized output) and ε = σ /√N, where σ = 1.5/N × Ni=1(yi −
y )2 and y is the value predicted by a 3-nearest neighbor algorithm. The kernel i
parameter (γ) produces the highest impact in the SVM performance, with values that are too large or too small leading to poor predictions. A practical method to set γ is to start the search from one of the extremes and then search towards the middle of the range while the predictive estimate increases
We will adopt the popular gaussian kernel, which presents less parametersthan other kernels (e.g. polynomial) [25]: K(x, x′) = exp(−γ||x − x′||2), γ > 0.Under this setup, the SVM performance is affected by three parameters: γ, ε andC (a trade-off between fitting the errors and the flatness of the mapping). To −ε 0 +ε Fig.2. Example of a multilayer perceptron with 3 inputs, 2 hidden nodes and one reduce the search space, the first two values will be set using the heuristics [4]:C = 3 (for a standardized output) and ε = σ /√N, where σ = 1.5/N × Ni=1(yi − y )2 and y is the value predicted by a 3-nearest neighbor algorithm. The kernel iparameter (γ) produces the highest impact in the SVM performance, with values that are too large or too small leading to poor predictions. A practical method to set γ is to start the search from one of the extremes and then search towards the middle of the range while the predictive estimate increases
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