Solving system of equations involving for loop.

Question

HUST Student 2018-6-11

0
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https://ww2.mathworks.cn/matlabcentral/answers/405063-solving-system-of-equations-involving-for-loop

回答： Jinal 2024-7-23

I'm trying to write a matlab (for loop) code to solve a system of equations eqn1 eqn2 eqn3 (get all solutions for the variables Z Q and F in the predetermined intervals) when parameter A varies in the range of 0 to 10. Then I would like to get the graphs: Z as a function of A; Q as a function of A; F as a function of A. Code that I produced

syms w e d n A Z F Q;
w=pi;
e=0.5;
d=10;
n=1;
eqn1 = Z+A.*w./(1-Q.*(1+e))*cos(F)==0;
eqn2 = cos(F+2.*Q.*n.*pi)+Z.*((e-Q.*(1+e))./A.*w)==0;
eqn3 = A-1/(2.*w.*abs(sin(Q.*n.*pi))).*(((1-e).*Z).^2+(d.*w+2.*(1+e).*(1-Q).*Q.*n.*pi.*Z).^2).^0.5==0;
equations = [eqn1 eqn2 eqn3];
vars = [A Z F Q];
range = [0 10;-40 40;0 6;NaN NaN];
for A=0:0.5:10;
    for i=1:5
    temp=vpasolve(equations, vars, range, 'random', true);
    sol(i,1)=temp.Z;
    sol(i,2)=temp.F;
    sol(i,3)=temp.Q;
    end
figure (1);
subplot(2,2,1)
plot(A,sol(i,1));
xlabel('A');
ylabel('Z');
subplot(2,2,2)
plot(A,sol(i,2));
xlabel('A');
ylabel('F');
subplot(2,2,3)
plot(A,sol(i,3));
xlabel('A');
ylabel('Q');
end