normal distribution recalcultation with a while loop

Hi there,

I am hav the following code

for i=1:lambda
    pop(i).Step=mvnrnd(zeros(VarSize),C{g});
    pop(i).Position=M(g).Position+sigma{g}*pop(i).Step.';
    pop(i).Cost=CostFunction(pop(i).Position);
    i=i+1;
end

I want thar if pop(i).Cost==0, the it restarts the calculations all over againg until I get a value different from 0, I am used to working with C++, where I would use a do while loop, but in matlab I am not sure how to do it,

I tried with a while loop after the previous piece of code, like this:

            for i=1:lambda
                pop(i).Step=mvnrnd(zeros(VarSize),C{g});
                pop(i).Position=M(g).Position+sigma{g}*pop(i).Step.';
                pop(i).Cost=CostFunction(pop(i).Position);        
                while pop(i).Cost ==0
                    pop(i).Step=mvnrnd(zeros(VarSize),C{g});
                    pop(i).Position=M(g).Position+sigma{g}*pop(i).Step.';
                    pop(i).Cost=CostFunction(pop(i).Position);  
                end
                i=i+1
            end

But it didnt work, any idea?

[Rik]

The for loop will increment your iterator for you, the while loop will not. The i=i+1; is not needed in the for loop (as mlint warns you). It is not clear to me what you're attempting to do, but if I understand your description, the code you've posted should do what you mean.

Answer 1

[Manikanta Aditya]

Hi,

The given snippet can be done without using while loop as well by simply using an if statement which when triggered reduces i by 1. This makes the loop to run again.

If you have to use while loop only, it can be done by initializing value of pop(i).Cost to 0, before the while loop and carrying out the problem inside the while loop.

Without while loop:

.

for i=1:lambda

pop(i).Step=mvnrnd(zeros(VarSize),C{g});

pop(i).Position=M(g).Position+sigma{g}*pop(i).Step.';

pop(i).Cost=CostFunction(pop(i).Position);

if pop(i).Cost == 0

i = i - 1;

end

end

With while loop:

.

for i=1:lambda

pop(i).Cost = 0;

while pop(i).Cost == 0

pop(i).Step=mvnrnd(zeros(VarSize),C{g});

pop(i).Position=M(g).Position+sigma{g}*pop(i).Step.';

pop(i).Cost=CostFunction(pop(i).Position);

end

end