Shade areas between graphs

I need to shade the areas of graph above y = 1 line and below y = -1 line. How can I do code for that.

Like this one.

Answer 1

[Sudheer Bhimireddy]

Look at area() function in MATLAB. May be that helps with your code.

Below is an example:

x        = -3*pi : 0.1 :3*pi; 
y_signal = sin(2*x)+sin(1.7*x);    % Random signal

threshold = 0.7;   % Area lower boundary

figure(1);
clf;

hold on;
area(x, max(y_signal, threshold), threshold,'EdgeColor', 'none', 'FaceColor', 'b'); 
plot(x, y_signal,'k-',lsz,2);

Here is the result:

[Sreerag K]

It worked very well in the positve y axis. But I need to do the same for the negative y axis which was not working with this code.

To do this same in the negative y axis what should I give as the baseline argument for area.

[Sudheer Bhimireddy]

I was able to replicate the problem with two baselines. For now, may be this workaround might help.

x        = -3*pi : 0.1 :3*pi; 
y_signal = sin(2*x)+sin(1.7*x);    % Random signal

threshold_high = 0.7;   
threshold_low  = -0.5;   

figure(1);
clf;

hold on;

area(x, max(y_signal, threshold_high), threshold_high,'EdgeColor', 'none', 'FaceColor', 'b'); 
area(x, min(y_signal, threshold_low),  threshold_low, 'EdgeColor', 'none', 'FaceColor', 'g'); 

% Now mask the unwanted region in between white
area([min(x) max(x)], [threshold_high threshold_high],threshold_low,'EdgeColor', 'none', 'FaceColor', 'w','ShowBaseLine', 'off'); 

plot(x, y_signal,'k-',lsz,2);
plot([min(x) max(x)], [threshold_high threshold_high],'k--',lsz,2);
plot([min(x) max(x)], [threshold_low  threshold_low], 'k--',lsz,2);

Output:

[Sreerag K]

Thank you. It worked fine