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HELP > Coding and Minimizing a Fitness Function Using the Genetic Algorithm > Minimizing Using Additional Arguments

Following line has been given, but it don't tell where to define these values? I tried to write in its fitness function and I tried to enter these values at different places in GA in matlab.

a = 100; b = 1; % define constant values

Please let me know, where to enter these constant values?

Answer 1

[Walter Roberson]

Define your function as taking two additional arguments, a, and b. Then when you call ga, instead of just giving a handle to your function, like

ga(@myObjectiveFunction, ....)

call

a = 100;
b = 1;
ga(@(x) myObjectiveFunction(x,a,b), .....)

See http://www.mathworks.com/help/matlab/math/parameterizing-functions.html

[Inderjeet Singh]

Program not running: -

I entered this code, it shows no errors: -

   function y = parameterized_fitness(x,a,b)
   y = a * (x(1)^2 - x(2)) ^2 + (b-x(1))^2;
   a=100;
   b=1;
   ga(@(x) parameterized_fitness(x,a,b));
end

In output I entered

Fitness function: @(x) parameterized_fitness(x,a,b)

Number of variables: 2

I get the following output: -

Optimization running.

Undefined function or variable 'a'.

I am new to matlab, please explain me how to do it right?

[Alan Weiss]

You put your ga call in your objective function. Don't do that. Do this instead:

   function y = parameterized_fitness(x,a,b)
   y = a * (x(1)^2 - x(2)) ^2 + (b-x(1))^2;
   end

Then in MATLAB, do this:

   a = 100;
   b = 1;
   [x,fval,exitflag] = ga(@(x)parameterized_fitness(x,a,b),2);

Alan Weiss

MATLAB mathematical toolbox documentation

[Inderjeet Singh]

I have inserted an image. I wrote it in fitness function and it still gives error: -

Error in fitnessfcn: Error: The expression to the left of the equals sign is not a valid target for an assignment.

I tried to enter value of a and b in linear inequalities, it still gave same error.

[Inderjeet Singh]

I tried to write it in matlab as shown in image and it gave errors too.

[Alan Weiss]

You saw that the first time you ran the code it worked fine. You saw that the second time there was an error. What was the difference between these two times? Look hard at the end of the ga call, you will see that the time it worked was when you had a ,2 toward the end of the line. What does this 2 mean? Look at the syntax for ga and see if you can figure it out.

Alan Weiss

MATLAB mathematical toolbox documentation