MATLAB: How I make the plot like this

Question

I want to draw this plot but I don't know how check the point (2pi,-2) and (6pi,4) (like that , the Solid line)

please help me…!!

Answer 1

This should get you started:

x = linspace(0, 10*pi);                                                 % Create Data

y = sin(x*0.3) + randn(size(x))/10;                                     % Create Data
y2pi = interp1(x, y, 2*pi);                                             % Interpolate To Find ‘y=2*pi’
y6pi = interp1(x, y, 6*pi);                                             % Interpolate To Find ‘y=6*pi’
figure
plot(x, y)
hold on
plot(xlim, [0 0], '-k', 'LineWidth',2)
plot([0 2*pi], [1 1]*y2pi, '--k',  [1 1]*2*pi, [0 1]*y2pi, '--k')
plot([0 6*pi], [1 1]*y6pi, '--k',  [1 1]*6*pi, [0 1]*y6pi, '--k')
hold off
% set(gca, 'XAxisLocation','origin')
text(2*pi, y2pi, '2\pi', 'HorizontalAlignment','center', 'VerticalAlignment','bottom', 'FontSize',15)
text(6*pi, y6pi, '6\pi', 'HorizontalAlignment','center', 'VerticalAlignment','top', 'FontSize',15)

You will have to experiment with your own data, and probably adjust the 'VerticalAlignment' values in the text calls.. However this will do all the calculations and the plotting.