clear clc close all syms xsym ysym %% 2.4 f1 = (ysym - 4 * xsym^2)^2 + (1 - xsym)^2; [x1, xs1, ~] = trust_region(f1, 2, 1, 0.2, [0;0], 1e-8, 1000); %% 2.4c - Energy function plot surf_iterates(f1, xs1, -0.25:0.01:1.25, -0.5:0.01:4.25); exportgraphics(gca,'2-4-energy.png', 'Resolution', 200); figure; %% 2.5 - Rosenbrock's function f2 = (1 - xsym)^2 + 100 * (ysym - xsym^2)^2; [x2, xs2, gnorms2] = trust_region(f2, 2, 1, 0.2, [0;0], 1e-8, 1000); %% 2.5b - Energy function plot surf_iterates(f2, xs2, -0.25:0.01:1.25, -0.25:0.01:1.25); exportgraphics(gca,'2-5-energy.png', 'Resolution', 200); %% 2.5c - Log gradient norms figure; semilogy(0:size(gnorms2, 2)-1, gnorms2, '.-k'); exportgraphics(gca,'2-5-gnorms.png', 'Resolution', 200); %% Helper functions function surf_iterates(f, xs, xrange, yrange) fl = matlabFunction(f); Z = zeros(size(yrange,2), size(xrange,2)); for x = 1:size(xrange, 2) for y = 1:size(yrange, 2) Z(y,x) = fl(xrange(x), yrange(y)); end end surf(xrange, yrange', Z, 'EdgeColor', 'none', 'FaceAlpha', 0.4); yrange = zeros(1, size(xs, 2)); for i=1:size(xs, 2) yrange(1, i) = fl(xs(1, i), xs(2, i)); end hold on plot3(xs(1, :), xs(2, :), yrange, '.r-'); plot3(xs(1, 1), xs(2, 1), yrange(1), '.w-'); plot3(xs(1, size(xs,2)), xs(2, size(xs,2)), yrange(size(xs,2)), '.k-'); hold off end