double forloop and plotting

Hi, I’m stuck on using ‘double forloop’

I got each ’all_K_db{i}’ corresponding to ‘e_1value’

and I want to get solutions and plot them in a (time, state x) graph.

As there are 5 values for ’all_K_db{i}’ and 2 values for ‘x=(x1,x2)’, 10 lines should exist on a plot. How can I show all the lines in one graph?

even if the code doesn't make any error, I can't check all(10lines) values of x=(x1,x2), I only see 2lines

%Figure2-2,data-based
e_1value=0.01:0.5:2.01;
numb_t = length(e_1value);%5
x1=[1; 1];
tspan = (1:2:15);
for tid=1:2:15
for i=1:numb_t
    
    A= [0.2, 1.3; 0.1, 1.2];
    B= [1; 2];
    D= [0.45 0.45; 0.3 -0.3];
    dxdt =@(t,x) A*x+ B*(all_K_db{i})*x+ D*x*(all_K_db{i})*x;
end
[t,x] = ode45(dxdt, tspan, x1);
end

[Junhwi Mun]

I also used 'all_x{tid}=x;' right after [t,x] = ode45(dxdt, tspan, x1);, but every 'all_x{tid}=x' has the same values for (x1,x2)

[Rik]

You are overwriting all your results in each loop.

Answer 1

[Ayush Gupta]

The problem is here that you are overwriting values when you use

[t,x] = ode45(dxdt, tspan, x1); 

As this line is outside of the second loop, only one dxdt value is returned and since the first/outside loop runs one time, it stores only 2 values and therefore you can see only 2 lines instead of 10. Correct version of this will be the following:

%Figure2-2, data-based

e_1value=0.01:0.5:2.01;

numb_t = length(e_1value);%5

x1=[1; 1];

tspan = (1:2:15);

for tid=1:2:15
    
    for i=1:numb_t
        
        A= [0.2, 1.3; 0.1, 1.2];
        
        B= [1; 2];
        
        D= [0.45 0.45; 0.3 -0.3];
        
        dxdt =@(t,x) A*x+ B*(all_K_db{i})*x+ D*x*(all_K_db{i})*x;
        
        [t,x] = ode45(dxdt, tspan, x1);
        
    end
    
end