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

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!

[Rik]

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.

Answer 1

[Jan]

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.

[David Goodmanson]

I suspect this is just a case of 'order(Trial) > 5' being an intended comment and lacking a % in front of it.

[Jan]

@David: Maybe, but this would not match the else-condition of "order(Trial) < 6".

[Rik]

It does for integers, which a variable called order may be presumed to contain. I would go for >=6, but this should work equally well.

[M Min]

Yes, that's my error so I changed the code to

elseif order(Trial) > 5;

but it is still not working fine.

[M Min]

I also tried to change it into

if order(Trial) <= 5;
...
elseif order(Trial) >= 6

but it is not working neither.

[M Min]

Specifically, those conditions work only for its first iteration and from second iteration, there are problems.

[M Min]

Oh I am really sorry but I missed to note about

order

I edit the post. Sorry again.

Answer 2

[M Min]

Finally I got what the problem is and it is not because of Tic and Toc as Rik, David, and Jan answered. I should have written

Key(Trial)

not

Key

Thank you for your answers. Appreciate!