double forloop and plotting

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Junhwi Mun
Junhwi Mun on 9 Jun 2020
Edited: madhan ravi on 12 Jun 2020
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
  2 Comments
Rik
Rik on 9 Jun 2020
You are overwriting all your results in each loop.

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Accepted Answer

Ayush Gupta
Ayush Gupta on 12 Jun 2020
Edited: madhan ravi on 12 Jun 2020
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

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