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Natalia
Natalia on 3 Feb 2012
Edited: Matt J on 1 Oct 2013
Hello! I have a function:
function z=my_fun(x)
a=2;
b=3;
c=1;
z=a*x(1)-b*x(2)+c*x(3);
I use the genetic algoritm (ga, gatool) to generate input parameters x(1), x(2) and x(3). It is necessary for me, that x(1)<x(2)<x(3). How and where can I set this constraint? Thank you very much for any answer :)
Natalia

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Accepted Answer

Sean de Wolski
Sean de Wolski on 3 Feb 2012
Interesting idea. This should be possible, probably with non-linear constraint option.
However, (disclaimer: this is just a thought/curiosity, no guarantees at all), what if you just sort x at the beginning of my_fun()? This would enforce the constraint in your fitness function and possibly cause convergence of the guesses. Let me know if/how it works for you.
function z=my_fun(x)
x = sort(x);
a=2;
b=3;
c=1;
z=a*x(1)-b*x(2)+c*x(3);
  2 Comments
Natalia
Natalia on 4 Feb 2012
Yes, it works. But if I have more input parameters and more constraints (for example: x(1)<x(2)<x(3), x(5)<x(4)<x(1)) sort will not help.
I think it linear constraint (this is just a thought/curiosity too).
If x(1)<x(2)<x(3)
hence:
x(1)<x(2);
x(2)<x(3);
x(1)<x(3);
hence:
1*x(1)-1*x(2)+0*x(3)<0;
0*x(1)+1*x(2)-1*x(3)<0;
1*x(1)+0*x(2)-1*x(3)<0;
If A*x<b,
hence:
A=[1 -1 0; 0 1 -1; 1 0 -1]
b=[0;0;0]
I try to use it. And it works... What do you think about it?
Sean de Wolski
Sean de Wolski on 6 Feb 2012
Yes, that looks good, I guess it is a linear constraint.

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