% gradient descent demo
% fred park
% whittier college 2019

%quadratic 1d gradient descent

close all; clear all; clc;

x = linspace(-5,5,100);
N = 20;

y = @(x) x.^2;
dy = @(x) 2*x;
delta = 0.1;
x1 = 5;
plot(x,y(x),'b-','LineWidth',3); hold on; plot(x1,y(x1),'d','markersize',15,'MarkerFaceColor','magenta'); hold off
pause

for i = 1:N
    x1 = x1 - delta*dy(x1)
    plot(x,y(x),'b-','LineWidth',3); hold on; plot(x1,y(x1),'d','MarkerSize',15,'MarkerFaceColor','magenta'); hold off
    pause
end