Supplied objective function must return a scalar value
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I have to minimize a function with FMINCON:
f = @(x,y) k*x.*(teta_in-y)
i create this script to apply fmincon:
x0 = [2000,10];
A = [1 0;0 -1];
b = [25;2273];
f = cell(2,1)
f{1} = @(x) k*x.*(teta_in-y)
f{2} = @(x) k*x.*(teta_in-y)
[xmin,fval] =fmincon(f,x0,A,b)
But the programme give me the error: Supplied objective function must return a scalar value
If you have a different way to minimize that function with fmincon i appreciate that
2 个评论
Dyuman Joshi
2024-1-8
编辑：Dyuman Joshi
2024-1-8
What are the values of k and teta_in?
Why do you use the same function twice?
Also, share the mathematical definition of the objective function you have to minimize.
EDOARDO GELMI
2024-1-8
采纳的回答
The function needs to return one parameter vector. One way to do that is to create a second function to map the inpouts to to such a vector:
ffcn = @(b)f(b(1),b(2));
Then, providing random values for the missing constants ‘k’ and ‘teta_in’ and running it produces —
k = rand
teta_in = rand
f = @(x,y) k*x.*(teta_in-y);
ffcn = @(b)f(b(1),b(2));
x0 = [2000,10];
A = [1 0;0 -1];
b = [25;2273];
[xmin,fval] =fmincon(ffcn,x0,A,b)
.
11 个评论
EDOARDO GELMI
2024-1-8
EDOARDO GELMI
2024-1-8
"what @(b) stands for?"
It's a placeholder. You can use any valid variable instead.
"Why i cannot use @(x) f(x(1),x(2))?"
You can. But since you have used x already in defining f before, to avoid confusion a different placeholder is used.
k = rand
teta_in = rand
f = @(x,y) k*x.*(teta_in-y);
ffcn = @(x)f(x(1),x(2));
x0 = [2000,10];
A = [1 0;0 -1];
b = [25;2273];
[xmin,fval] =fmincon(ffcn,x0,A,b)
EDOARDO GELMI
2024-1-8
Torsten
2024-1-8
You can. But since you have used x already in defining f before, to avoid confusion a different placeholder is used.
b is also in use :
b = [25;2273];
:-)
Dyuman Joshi
2024-1-8
@Torsten, I meant x as a placeholder, whereas b is a variable, but your point is valid nonetheless.
Best to use different names (as much as possible) to avoid confusion.
Matt J
2024-1-8
Understood, thank you very much for the explanation!
@EDOARDO GELMI If so, and everything is clear now, you should Accept-click the answer
EDOARDO GELMI
2024-1-8
Star Strider
2024-1-8
Thank you!
In:
ffcn = @(b)f(b(1),b(2));
the ‘b’ argument is local to the function, and does not refer to any other value outside it. (I generally use ‘b’ for parameters because standard optimisantion convention is to define parameters as β, however any variable that makes sense in the context would work.)
.
EDOARDO GELMI
2024-1-8
Star Strider
2024-1-8
As always, my pleasure!
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