MATLAB: Do two functions in the plot “switch” positions when plotted

plot

Here is my code:
clear
clc
m1 = 1;
m2 = 2;
m3 = 1;
k1 = 2000:8000;
k2 = 2000;
k3 = 6000;
M = [ m1 0 0; 0 m2 0; 0 0 m3]
for n = 1:length(k1);
    K = [k1(n)+k2 -k2 0; -k2 k2+k3+3 -k3; 0 -k3 k3];
      EV = eig(-inv(M)*K);
      w1(n) = sqrt(abs(EV(1)));
      w2(n) = sqrt(abs(EV(2)));
      w3(n) = sqrt(abs(EV(3)));
end
figure(1)
plot(k1,w1/(2*pi),k1,w2/(2*pi),k1,w3/(2*pi))
legend w1 w2 w3
title('Varying k1')
ylabel('Frequency (Hz)')
xlabel('k1')
my plot looks like the picture attached. I cannot figure out why w2 and w3 seem to jump to one another after about 7000.
How can I resolve this?

Best Answer

EIG doesn't guarantee it always returns the eigenvalues in any particular order. If you want them to always be returned in increasing order or always in decreasing order, SORT them.
Related Question