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lsqnonlin with vector input and multiple equations.

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Emma Van Puyenbroeck
Emma Van Puyenbroeck el 21 de Feb. de 2020
Respondida: Pravin Jagtap el 24 de Feb. de 2020
when I try to run my model I always receive the error 'Undefined function or variable 'x'.'
How should I specify my variable x?
function y=testst(T_1,T_2,P_c,Q_gen)
x_1=0.35
x_2=0.21
y_3=0.85
h_1=1500
h_2=500
h_3=230
f(1)=x(1)-x(2)-x(3);
f(2)=x_1*x(1)-x_2*x(2)-y_3*x(3);
f(3)=Q_gen+x(1)*h_1-x(2)*h_2-x(3)*h_3;
steadystate=@(x) f(x);
st=[0.005 ;0.005; 0.005]';
lb=[0; 0 ;0];
ub=[1 ;1 ;1];
x=lsqnonlin('steadystate',st,lb,ub)
y=x
end
I also tried this:
st=[0.005 ;0.005;0.005];
lb=[0; 0 ;0];
ub=[1 ;1;1];
y=lsqnonlin(@(x) steadystate(x,x_1,y_3,h_1,h_2,h_3,Q_gen),st,lb,ub);
function f= steadystate(x,x_1,x_2,y_3,h_1,h_2,h_3,Q_gen)
f(1)=x(1)-x(2)-x(3);
f(2)=x_1*x(1)-x_2*x(2)-y_3*x(3);
f(3)=Q_gen+x(1)*h_1-x(2)*h_2-x(3)*h_3;
end
but than I had 'not enough input arguments'

Respuestas (1)

Pravin Jagtap
Pravin Jagtap el 24 de Feb. de 2020
Hello Emma,
The error mentioned is caused because of the way 'function handle' is used (steadystate=@(x) f(x);). In your case, it is better to write the separate function which returns 'f(1)', 'f(2)' and f(3) values. Please refer to the following example for creating the function handle:
function f = get_f(x)
f(1) = x(1);
f(2) = x(2);
f(3) = x(3);
end
Then, run the following script to see how to create the function handle:
f = @get_f;
x = [1 2 3];
steadystate = f(x)
Here, ‘steadystate’ will be 1x3 vector. Modify your code using above reference and for more details on how to use function handles use the following documentation link:

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