(HOW) I need the code run again if the ( else condition return ) till give me value

Question

Njud Alotaibi 2021-9-27

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评论： Njud Alotaibi 2022-2-3

Hi all. I have my code, and if the "if" condition is false for any value of i or j then it should stop and do the function again until the if condition true for all the values for i and j.

After else there is a return but it stops running and I run it again to get the (bestsol value) which do (Do this command line) and for loop again from the beginning. I need this code to run until I get (bestsol value) without it returning early.

I have used while true but it keeps running. Also I used while Halt==1 but work as no while loop.

function Labelvertices
%DO THIS LINES 
%-----
%-----
%----
%-----Do this command line-------
verticeslabe=[0,randi(7)];
makematrix % it is function give us the matix d
for i= 1:7
     for j=1:7
         if (i~=j)
            if % codition 1 met  || codition 2 met 
                  verticeslabe(i)= % do this;
                  verticeslabe(j)= % do this;
            else 
              % does not meet codition 1 OR codition 2  go return to (do this command line) and do for loop again till we have (bestsol)
              return ; 
            end
         end   
     end                  
end        
bestsol=verticeslabe(:,1:7) % this values i need it 
end

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Rik 2021-9-27

Return will exit the function, not just a loop.

Your code is too compact now. E.g. makematrix is either not a function, or you're not storing the result.

Perhaps you want to make your nested loop a subfunction that returns a second output: a valid flag. That way you can use a while loop and repeatedly call this until the flag is true.

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Answer 1

Image Analyst 2021-9-27

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https://ww2.mathworks.cn/matlabcentral/answers/1461309-how-i-need-the-code-run-again-if-the-else-condition-return-till-give-me-value#answer_796299

编辑：Image Analyst 2021-9-28

在 MATLAB Online 中打开

Try this when you define it:

function success = Labelvertices
success = true;
% existing code....
% Then inside the else where it fails, set success equal to false.  New code:
success = false;
return;

Now when you call it use a while loop, use code like this:

success = false
loopCounter = 1;
maxIterations = 100; % Failsafe - way more than you think it should ever take.
while ~success && loopCounter <= maxIterations
    success = Labelvertices;
    if success
        % It worked so we can quit now.
        break;
    end
    loopCounter = loopCounter + 1;
end
% Alert user if it never succeeded.
if loopCounter >= maxIterations
    warningMessage = sprintf('WARNING: the process did not succeed after %d attempts!', loopCounter - 1);
    uiwait(warndlg(warningMessage));
end

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Njud Alotaibi 2022-2-3

Thank you so much

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Answer 2

Walter Roberson 2021-9-27

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https://ww2.mathworks.cn/matlabcentral/answers/1461309-how-i-need-the-code-run-again-if-the-else-condition-return-till-give-me-value#answer_796304

在 MATLAB Online 中打开

do_again = true;
while do_again
  do_again = false;
  for i= 1:7
     for j=1:7
         if (i~=j)
            if % codition 1 met  || codition 2 met 
                  verticeslabe(i)= % do this;
                  verticeslabe(j)= % do this;
            else
                do_again = true;
                break
            end
         end
     end
     if do_again; break; end
  end
end

If the else is never executed, then do_again will not be set back to false, and the while loop will finish.

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Image Analyst 2021-9-28

How do you guard against an infinite loop?

Walter Roberson 2021-9-28

The user requirements are clear, 'if the "if" condition is false for any value of i or j then it should stop and do the function again until the if condition true for all the values for i and j' . Stopping the function any time before the condition is true for all members of the array is contrary to the requirements to keep going until the condition is true for all the values for i and j -- even if that takes thousands of years.

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