Two Signals on one graph? Difference between two signals?

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Marwan
Marwan le 21 Juil 2011
Commenté : Walter Roberson le 24 Mai 2017
Hello all;
I am working on two EEG signals (channel 5 & channel 13): f_c5(j,:) =abs(fft(t5(j,:),L)); f_c13(j,:) =abs(fft(t13(j,:),L));
And I am trying to find an equation that allow me to draw both signal on the same graph.
Also I would like to draw a graph presenting the difference between both of them.
Does anybody have any idea about it?
Many Thanks, Marwan

Réponses (3)

the cyclist
the cyclist le 21 Juil 2011
Here are two ways.
x = 1:10;
y1 = 2*x;
y2 = 3.5*x;
% Multiple plot commands, with "hold" on
figure
hold on
plot(x,y1,'r');
plot(x,y2,'b');
plot(x,y2-y1,'g');
% Multiple lines in one plot command
figure
plot(x,y1,x,y2,x,y2-y1);

Murthy
Murthy le 14 Sep 2011
Hi.
What should we do when y1 and y2 are not defined on common x but different x values. Say x1= 1:10:100; and x2 = 0.1:0.05:300
How can I plot the difference of y1 and y2?
  2 commentaires
Jan
Jan le 14 Sep 2011
Simply fill the shorter of y1 or y2 with NaNs, such that both vectors have the same size again.
Walter Roberson
Walter Roberson le 14 Sep 2011
Jan, if the x coordinates are not aligned on the same interval, subtraction is not going to be meaningful.
Murthy, you will need to interpolate (such as by using interp1()) to a common interval over the shared range and do the subtraction on the interpolated data. In the particular example you give, the interpolation could be done by subsampling of x2, x2(1*20:10*20:100*20) but it would be easy to construct examples where interp1() was needed.

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Meth Hathemi
Meth Hathemi le 24 Mai 2017
hello Sir i have a simulate problem could you find a solution and send me the code of arduino board and matlab? PLEASE methlouthihathemi@gmail.com

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