A support vector machine (SVM) is a supervised model for classification and regression. It provides a strong off-the-shelf baseline and can represent nonlinear relationships with kernels such as the radial basis function (RBF) and polynomial kernels. section 1.3 section 1.3.2
SVM training balances fit against regularization. The parameter C controls that balance: small values favor flatter, simpler models that may underfit, while large values prioritize training error and can produce complex models that overfit. section 1.3.2
Use the support-vector view carefully:
- Support vectors are the smaller working set of training examples on which the model depends. section 1.3.2
- The number of support vectors does not directly measure model complexity, because restrictive small C values can force the final model to use more vectors. section 1.3.2
- Compare training and test performance across C values rather than selecting a model from training fit alone. section 1.3.2
Tuning an SVR
With scikit-learn, create an RBF-kernel SVR and evaluate C across a logarithmic range using a validation curve and R² scores. On Friedman-1 regression data, increasing C improves training fit but can reduce generalization. section 1.3.2
Figure 1.5 Support vector machine with an RBF kernel, with kernel parameter gamma = 0.75. Small values of C result in more linear (flatter) and less complex models that underfit the data, while large values of C result in more nonlinear (curvier) and more complex models that overfit the data. Selecting a good value for C is critically important in training a good SVM model.
Visualizes how C changes an RBF-kernel SVM from flatter, more linear fits toward curvier, more complex fits. section 1.3.2




