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49 lines
1.4 KiB
Matlab
49 lines
1.4 KiB
Matlab
10 years ago
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function plotDecisionBoundary(theta, X, y)
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%PLOTDECISIONBOUNDARY Plots the data points X and y into a new figure with
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%the decision boundary defined by theta
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% PLOTDECISIONBOUNDARY(theta, X,y) plots the data points with + for the
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% positive examples and o for the negative examples. X is assumed to be
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% a either
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% 1) Mx3 matrix, where the first column is an all-ones column for the
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% intercept.
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% 2) MxN, N>3 matrix, where the first column is all-ones
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% Plot Data
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plotData(X(:,2:3), y);
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hold on
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if size(X, 2) <= 3
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% Only need 2 points to define a line, so choose two endpoints
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plot_x = [min(X(:,2))-2, max(X(:,2))+2];
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% Calculate the decision boundary line
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plot_y = (-1./theta(3)).*(theta(2).*plot_x + theta(1));
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% Plot, and adjust axes for better viewing
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plot(plot_x, plot_y)
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% Legend, specific for the exercise
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legend('Admitted', 'Not admitted', 'Decision Boundary')
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axis([30, 100, 30, 100])
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else
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% Here is the grid range
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u = linspace(-1, 1.5, 50);
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v = linspace(-1, 1.5, 50);
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z = zeros(length(u), length(v));
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% Evaluate z = theta*x over the grid
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for i = 1:length(u)
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for j = 1:length(v)
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z(i,j) = mapFeature(u(i), v(j))*theta;
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end
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end
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z = z'; % important to transpose z before calling contour
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% Plot z = 0
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% Notice you need to specify the range [0, 0]
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contour(u, v, z, [0, 0], 'LineWidth', 2)
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end
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hold off
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end
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