Tic Toc seems disturb the operation of if-else function in the for-loop

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M Min 2017-4-18

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/335981-tic-toc-seems-disturb-the-operation-of-if-else-function-in-the-for-loop

回答： M Min 2017-4-19

Hi,

I put the function tic and toc in the for loop but it looks that it disturb the working of if-else function in the same loop. Below is my code.

A = 10;
order = randperm(A);
for Trial = 1:A;
    ImageOrder = [num2str(order(Trial)) '.jpg'];
        IMG = imread(ImageOrder);
        imshow(IMG); 
    Start = tic;
    k = waitforbuttonpress;
    Key(Trial) = double(get(gcf,'CurrentCharacter'));
    if order(Trial) < 6;
        if  Key == 28
            IMG_X = imread('x.jpg');
                imshow(IMG_X);
                pause(1);
        end
    else order(Trial) > 5;
        if  Key == 29
            IMG_X = imread('x.jpg');
                imshow(IMG_X);
                pause(1);
        end
    end 
    Elapsed(Trial) = toc(Start);
end

Before I put Tic and Toc in the for-loop, if-else functions were working fine, but now they are not working. Is it correct that tic and toc disturb the operation of if-else? Thanks!

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Rik 2017-4-18

I don't any reason why this would be the case. Sometimes old variables can stick around longer than they should, which may cause unexpected results. You can avoid this by using functions instead of scripts, or (if you have a VERY good reason not to use functions) clear variables.

If you already this either of these, I don't have an explanation.

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Answer 1

Jan 2017-4-18

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/335981-tic-toc-seems-disturb-the-operation-of-if-else-function-in-the-for-loop#answer_263512

编辑：Jan 2017-4-18

在 MATLAB Online 中打开

No, tic/toc does not influence the if command. This is a magic idea and Matlab does not do such strange things. Otherwise you could not use Matlab for predicatble results.

The code contains another problem:

    if order(Trial) < 6;
      ...
    else order(Trial) > 5;
      ...
    end

This is equivalent to:

    ...
    else
      order(Trial) > 5;
      ...

This compares the value of order(Trial) with 5, but ignores the result. Do you mean:

elseif order(Trial) > 5;

?

Seeing this problem, I'm convinced that tic/toc did not chnage anything. Try it by your own: comment the tic/toc lines and check, if this changes anything. Then fix the "elseif" problem and check it again.