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Table 2 The four basic kernel functions

From: Exploring the potential of 3D Zernike descriptors and SVM for protein–protein interface prediction

Kernel name Mathematical formulation
Linear \(K(\boldsymbol {x}_{i}, \boldsymbol {x}_{j})=\boldsymbol {x}_{i}^{\intercal } \boldsymbol {x}_{j}\)
Polynomial \(K(\boldsymbol {x}_{i}, \boldsymbol {x}_{j})=\left (\gamma \boldsymbol {x}_{i}^{\intercal } \boldsymbol {x}_{j} + r\right)^{d}, \gamma > 0\)
Radial basis function (RBF) K(x i ,x j )=exp(−γx i x j 2),γ>0
Sigmoid \(K(\boldsymbol {x}_{i}, \boldsymbol {x}_{j})=\text {tanh}\left (\gamma \boldsymbol {x}_{i}^{\intercal } \boldsymbol {x}_{j} + r\right), \gamma > 0\)
  1. γ, r and d are kernel parameters