System of Nonlinear equations-Conversion to logical from sym is not possible.

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Tanjina
Tanjina 2013-10-10
评论： Matt J 2013-10-10
Hello everyone,
I am a very new user of MATLAB. I am trying to solve system of equation contain linear and non linear equation.
syms x1 x2 x3 x4 x5 x6 x7
EQ1 = x1-x2-x6;
EQ2 = x2+x3-2;
EQ3 = x4+x5-x3;
EQ4 = x7+x6-x4;
EQ5 = -K2*x2*abs(x2)+K3*x3*abs(x3)+K4*x4*abs(x4)+K6*x6*abs(x6);
EQ6 = 5-K5*x5*abs(x5)-K3*x3*abs(x3)+K2*x2*abs(x2)+K1*x1*abs(x1);
EQ7 = 5-K1*x1*abs(x1)-K6*x6*abs(x6)+K7*x7*abs(x7)-(22.9-10.33*x7^2+2.823*x7)*(x7/abs(x7));
sol = solve(EQ1, EQ2, EQ3, EQ4, EQ5, EQ6, EQ7);
sol.x1
sol.x2
sol.x3
sol.x4
sol.x5
sol.x6
sol.x7
xn(1)=x1;
xn(2)=x2;
xn(3)=x3;
xn(4)=x4;
xn(5)=x5;
xn(6)=x6;
xn(7)=x7;
for i = 1: N
Error = abs((xn(i)-x(i))/x(i)) ;
if Error > Error_max
Error_max= Error;
end % if
end
This algorithm run for one time and give result for x1,x2......x7 but it does not calculate any error and gives me this message.
"Conversion to logical from sym is not possible.
Error in again (line 118) if Error > Error_max"
I don't understand how can I solve it. It will be great help if someone can help me.
Regards, Tanjina

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回答（1 个）

Matt J
Matt J 2013-10-10
Error and Error_max are sym variables, so the logical expression
Error > Error_max
cannot be evaluated.

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