MATLAB: How to plot all iterations of the for loop

2d plotfor loop

Hey I'm kind of new to MALAB, so bear with me please!
I'm trying to plot the real and imaginary parts of the eigenvalue results in my for loop, as a function of I from [0,4].
Here's my code:
figure
hold on
for I = 0:0.1:4
    p = [-1/3 0 -1 (I-2)]
    r = roots(p)
    x = r(3)
    A = [(1 - x^2) -40 ; 1/800 -1/40]
    e = eig(A)
    plot(I,real(e(1)),'r-',I,imag(e(1)),'b-')
end
My plot keeps coming up empty, and no error shows up. what can i do?

Best Answer

Right now, each plot is plotting only one point. To achieve the behavior you want, create the vectors and plot them outside the for loop
figure
hold on
e=[];
for I = 0:0.1:4
    p = [-1/3 0 -1 (I-2)]
    r = roots(p)
    x = r(3)
    A = [(1 - x^2) -40 ; 1/800 -1/40]
    e = [e,eig(A)]
end
 plot(0:0.1:4,real(e(1,:)),'r-',0:0.1:4,imag(e(2,:)),'b-')
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