Data Analysis with R, Second Edition - Second Edition

The diagonal decision boundary

The second dataset sports an optimal decision boundary that is a diagonal line—one that is not orthogonal to the axes. Here, we start to see some cool behavior from certain classifiers:

Figure 10.13: A plot of the decision boundaries of our four classifiers on our second contrived dataset

Though all four classifiers were reasonably effective in this dataset's classification, we start to see each of the classifiers' personalities come out. First, the k-NN creates a boundary that closely approximates the optimal one. The logistic regression, amazingly, throws a perfect linear boundary at the exact right spot.