Plot results of ODES.

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Marios Christofides 2020-7-9

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https://ww2.mathworks.cn/matlabcentral/answers/562430-plot-results-of-odes

评论： James Tursa 2020-7-9

I'm trying to model a PI and wanted to graph the results of the for loop that is solving the four ODEs. I'm not sure how to graph the results. Can anybody help?

hi1 = 0;

hi2 = 0;

hi3 = 5;

ys = 10;

u = 1;

Kc = 7.84;

ti = 4.424;

zi4 = 0;

f = 'Time'; g = 'h1'; h = 'h2'; p = 'h3'; r = 'u';

fprintf('Time \t h1\t h2\t \t h3 \t \t u\n', f, g, h, p, u)

t = 0;

fprintf('%5.2f \t %5.2f \t %5.2f \t %5.2f \t %5.2f\n',t,hi1,hi2,hi3,u );

for i = 1:2:10

%Forward Euler Method

u = Kc * (ys - hi3) + (Kc/ti)*zi4;

h1 = (1/10)*dt*(u - (hi1));

h2 = (1/2)*dt*(hi1-hi2);

h3 = dt*((hi2-hi3));

z4 = ys - hi3

hi1 = h1;

hi2 = h2;

hi3 = h3;

zi4 = z4;

fprintf('%5.2f \t %5.2f \t %5.2f \t %5.2f\n',t,h1,h2,h3,u);

end

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Marios Christofides 2020-7-9

I didn't use ODE45 and I don't know how to do it using a for loop.

James Tursa 2020-7-9

Store your intermediate results (the values in the loop) in arrays. Then after the loop you can plot them.

Can you post the four differential equations you are solving? Your Euler method looks a bit strange and I would like to check your code against the equations.

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