waitbar within a while loop

Hi,

I have a code that need to necessary execute a "while" loop. I am wondering how is possible to use a wait bar until this while loop finishes ?

Thanks

Answer 1

[Brendan Hamm]

Right from the documentation waitbar :

    h = waitbar(0,'Please wait...');
    steps = 1000;
    for step = 1:steps
        % computations take place here
        waitbar(step / steps)
    end
    close(h)

[msh]

Thanks, but I never understood this documentation that's why I thought to ask. In a particular part of my code, there is a while loop

    while > crit
       do some stuff
    end

this while loop I don't know when it finished, it might need 1000 or it might need 10000 iterations. I cannot tell in advance or guess how many iterations the while loop needs in order to stop.

what I am interested however, is to see a wait bar once my code enters this particular while loop and closes once the while loop stops.

So, I cannot really understand how to apply what in the documentation is suggesting, which refers to "for loop" with predetermined steps while in my case I have a "while" loop with unknown iterations.

[Brendan Hamm]

Well now that you have changed the question in regards to a while-loop, the answer is that there is now way you can show the progress if you are not sure how many iterations will take place. There are of course exceptions to this depending on the criteria of your while loop. For instance if you are doing something which is converging on every iteration you could use the convergence rate for the waitbar.

[David J. Mack]

I agree with Brendan. The definition of the while loop is that you do not know how many steps it will take to finish (if you do, you can use a for-loop instead). Therefore, you will not be able to show the progress. Even when using convergence rate as a proxy for the steps, you are misleading the user, as an increase from 0 to 1 % might take MUCH less time than an increase from 98 to 99 %.

Answer 2

[Chintan Joshi]

I recently wanted to do it. Here's how I managed it. But you will need a counter. Below K is some vector being updated at each iteration.

c = 0;
h = waitbar(0,'Please wait...');
while c <= length(K)
  steps = length(K);
  % complex computations taking place! :)
  c = c+1;
  waitbar(c / steps);
end
close(h);

[David J. Mack]

Not to be picky, but this is just the for-loop mentioned by Brendan dressed in while (ignoring the index initialization error):

    h = waitbar(0,'Please wait...');
    steps = length(k);
    for c = 1:steps
        % computations take place here
        waitbar(c / steps)
    end
    close(h)

[Brendan Hamm]

I wouldn't say this is picky. You are educating on the appropriate usage of for loops vs while loops and possibly removing any further confusion. This is simply correct!