How do I plot datas from the variable matrix.

Hello,

I am trying to solve below problem;

"Using MATLAB, investigate the nature of the variation of the principal values and directions over the interval 1 < x1 < 2. Formally plot the variation of the absolute value of each principal value over the range 1 < x1 < 2."

And here is what I've done so far:

clc;
clear all;
x=[1:0.1:2];
for i=1:length(x)
A(i,:,:)=[2*i,i,0;i,-6*(i^2),0;0,0,5*i]
% Calculate Invariants
invariants(i)=[trace(A),(trace(A)^2-trace(A*A))/2,det(A)]
[V,L]=eig(A(i))
% Principal Values are the Diagonal Elements of the L Matix
principal_values(i)=abs([L(1,1),L(2,2),L(3,3)])
% Principal Directions are the Columns of the V Matrix
principal_directions(i)=[V(:,1),V(:,2),V(:,3)]
end

I was able to handle the calculation part. But I could not able to plot that.

I need to plot each data in "principal values" vector in the range of 1 < x <2.

The result will be like this:

Thank you in advance.

[KSSV]

Are you sure the above code is working?

[Yagiz Simsek]

No, its not working :) That is why asked the question actually. I couldn't figure it out how do I correctly edit it and plot it as I wanted. But if you delete all loop codes its working well for the calculate values.

Answer 1

[KSSV]

x=[1:0.1:2];
N = length(x) ;
P1 = zeros(N,1) ;
P2 = P1 ;
P3 = P1 ;
for i=1:N
    A=[2*x(i),x(i),0;x(i),-6*x(i)^2,0;0,0,5*x(i)] ;
    % Calculate Invariants   
    [V,L]=eig(A) ;
    % Principal Values are the Diagonal Elements of the L Matix
    P1(i) = abs(L(1,1)) ; 
    P2(i) = abs(L(2,2)) ;
    P3(i) = abs(L(3,3)) ;        
end
figure
hold on
plot(x,P1,'.-r') ;
plot(x,P2,'.-b') ;
plot(x,P3,'.-g') ;

legend({'Value 1', 'Value 2', 'Value 3'})

[Yagiz Simsek]

Thank you so much that is realy make sense right now :) Thank you