Cursera: machine learning ex6.

machine_learning/mlclass-ex6-008/mlclass-ex6/visualizeBoundary.m

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+function visualizeBoundary(X, y, model, varargin)
+%VISUALIZEBOUNDARY plots a non-linear decision boundary learned by the SVM
+%   VISUALIZEBOUNDARYLINEAR(X, y, model) plots a non-linear decision 
+%   boundary learned by the SVM and overlays the data on it
+
+% Plot the training data on top of the boundary
+plotData(X, y)
+
+% Make classification predictions over a grid of values
+x1plot = linspace(min(X(:,1)), max(X(:,1)), 100)';
+x2plot = linspace(min(X(:,2)), max(X(:,2)), 100)';
+[X1, X2] = meshgrid(x1plot, x2plot);
+vals = zeros(size(X1));
+for i = 1:size(X1, 2)
+   this_X = [X1(:, i), X2(:, i)];
+   vals(:, i) = svmPredict(model, this_X);
+end
+
+% Plot the SVM boundary
+hold on
+contour(X1, X2, vals, [0 0], 'Color', 'b');
+hold off;
+
+end