Nonlinear Optimization problem in Matlab

Hi

I hve problem when I use x(0) in nonlinear constraint in my code and I have to start with x(0)!.

Please, Could any one solve this issue. I have to solve it to find the lower and upper bounds.

THE ERROR:

[Torsten]

1, Array indices start at 1; thus x(0) will produce an error.

2. Put [] around the c-vector.

Best wishes

Torsten.

[Talal Alharbi]

Thank you Torston

If I put c=[] That mean the ((inequality constraints c)) is empty and I use this constraint to effect on my optimization problem to give me different results.

Your suggestion it works but without use this constraint.

[Stephan]

What Torsten meant was not:

c=[]

but

c=[x(1)...]

[Talal Alharbi]

Thank you Stephan

I should start from x(0) since The first row from the matrix is [1 1 1 1 1 1 1 1 1 1]

So, I cannot start from x(1).

[Torsten]

Shift all your x-indices by 1 - this will do the job:

objective = @(x) sum(x(2:end));

and

for i = 2:9
  c(i-1,1) = x(i)^2-x(i-1)*x(i+1);
end

[Talal Alharbi]

Thank you Torsten . I appreciate it.

Actually,I did this way before. But I try to get other results when I start from x(0) since I want to compare them with other studing. NOW, I conclude, I cannot get results from this situation if I start from x(0).

My concern now is how can I find the upper bound from this problem?

I try to change the objective function by multiplying it (-1) but it did not work and I got this error.

[Torsten]

It is impossible to load your screenshots into MATLAB.

So please include your complete code as plain text and use the CODE button to format it.

[Talal Alharbi]

I found the minimize, but I could not find the maximize for the same code, Could you help me, please?

[Torsten]

If you use

objective=@(x)  -(x(2)+x(3)+x(4)+x(5)+x(6)+x(7)+x(8));

you maximize the expression

x(2)+x(3)+x(4)+x(5)+x(6)+x(7)+x(8)

[TALAL ALHARBI]

Actually, I did but it does give me the different value.

[Torsten]

What do you mean by "different value" ? Different to what ?

[Talal Alharbi]

I attached the code. The problem when I try to find the upper bound (max) which after I multply by (-)

Answer 1

[David Wilson]

Are you confusing x0, the start guess with x(0), which does not exist. In your constraint, you write x(0). If that is really what you want, then you need to roll your indices on by one. But somehow I doubt it. If you hadpasted your code, I'd have taken a look at it.

[Talal Alharbi]

x0 it is ok , there is no effect of it. But (the maximize) I could not find it when I change the obejctive function to negative.

[Walter Roberson]

You assign the output of the first fmincon() call to a pair of variables named x and fmincon . When you do that, fmincon becomes a numeric scalar instead of a function, and the [x,fval] = fmincon(etc) that you have becomes a request to index into the scalar named fmincon and somehow return two different variables from that, which is not possible from an indexing operation.

[Talal Alharbi]

Ok, I got it. Thank you so much. :)