Shows sign of from si(2x) * cos(2x) in matlab

gistfile1.matlab

figure;

% sizes
y_size = 1.5;
x_size = 2*pi;

% colors
cos_col = 'c';
si_col = 'b';
sign_col = 'r';

% variables and functions
x = -x_size:0.00001:x_size;
cos_y = cos(2*x);
sinc_y = sinc(2*x/pi);
signs = sign(cos_y.*sinc_y);

% plot graphs
hold on;
h = plot(x,cos_y);
h2 = plot(x,sinc_y);
h3 = plot(x, signs);

% colors and axes
set(h, 'Color', cos_col);
set(h2, 'Color', si_col);
set(h3, 'Color', sign_col);
axis([-2*pi 2*pi -1.5 1.5]);
grid on;

% vertical bars in interval of stepzie
stepsize = pi/4;

for i= -x_size:stepsize:x_size
    line([i i], [-1 * y_size y_size], 'Color', [0.2 0.2 0.2]);
end

% some help text
xlabel('x');
ylabel('cos(gr?n) und si(rot)');
title('Phase-Sign');

text(-2, 1.25, 'cos(2x)', 'Color', cos_col);
text(-2, 1.15, 'si(2x)', 'Color', si_col);
text(-2, 1.05, 'sign(cos(2x) * si(2x))', 'Color', sign_col);

set(gca, 'XTick', -x_size:stepsize:x_size);

hold off;