While loop for a stopping criterion and check if it positive

Hello everyone,

Sorry if the title is not clear enough, it is quite hard to put in to simple word. In the current Matlab code I am working on, I have a while loop of the type:

while and(X > eps1, Y > eps2) && count < it_max
    %calculations
end

with X, Y the variables of interest; eps1, eps2 the stopping criterias. My problem is that eps1 and eps2 are positive, and X and Y can take negative values. However these must be positive and I would like to add a condition to make the while loop continue when X and Y are negative (without any absolute value function).

Thank you.

Answer 1

[Image Analyst]

I don't know why you don't want to use the abs() function but you can do it without it like this:

while ((X > eps1 && Y > eps2) || (X < eps1 && Y < eps2)) && count < it_max
    %calculations
    count = count + 1;
end

[Rémi BERNARD]

I give an example which is not my case but I think can illustrate it well. Let's say in this loop I can have viscosity, which cannot be negative but for computation purpose I say it can be.

So take eps = 0.1:

- if for a certain iteration, for example 5, I have my viscosity which is -0.06; with abs() my criteria is respected but the result is not physically acceptable. (ie Matlab accepts it but I don't)

- for iteration +1 I have viscosity = 0.05; so I would like to accept that result instead of the previous one.

Your code does more or less the same thing no?