MATLAB: Help solve a system of Differential Equations

Question

Hi everybody,

I have code to solve a system of Differential Equations with matrix. I do not know my mistakes. When I run my, error in my code " Undefined operator '*' for input arguments of type 'function_handle'.Error in osc (line 22) odes=diff(P)==(0.2*A+s*B)*P;"

Can you see it and help me fix it. Thanks so much!

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This is my code:

T=100; g=0.5*T; n=3;s0=0.5;lamda=0.2;
% khai bao ham xa xe (KNTH)
s=@(t)(s0).*(((t-floor(t/T)*T)<g))+(0)*(((t-floor(t/T)*T)>g));
t=linspace(0,500);
plot(t,s(t));
grid;
% Khai bao mt A vuong cap n+2
syms p1(t) p2(t) p3(t) p4(t) p5(t)
A=[-1 0 0 0 0;
    1 -1 0 0 0;
    0 1 -1 0 0;
    0 0 1 -1 0;
    0 0 0 1 0];
B=[0 1 0 0 0;
   0 -1 1 0 0;
   0 0 -1 1 0;
   0 0 0 -1 1;
   0 0 0 0 -1];
P=[p1; p2; p3; p4; p5];
odes=diff(P)==(0.2*A+s*B)*P;
[p1Sol(t),p2Sol(t),p3Sol(t),p4Sol(t),p5Sol(t)]=dsolve(odes);
C=P(0)==[1;0;0;0;0];
[p1Sol(t),p2Sol(t),p3Sol(t),p4Sol(t),p5Sol(t)]=dsolve(odes,C);
clf
fplot(p1Sol)
hold on
fplot(p2Sol)
hold on
fplot(p3Sol)
hold on
fplot(p4Sol)
hold on
fplot(p5Sol)
grid on
legend('p1Sol','p2Sol','p3Sol','p4Sol','p5Sol','Location','best')

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Answer 1

syms t
s = piecewise((t-floor(t/T)*T)<g,s0,0);
fplot(s, [0 500])
%do not do the numeric assignment to t

Note that you do did explicitly define s for the case where the expression exactly equals g, but the numeric logic you used would have come out as 0 for that case anyhow.