IF inside FOR loop in Matlab doesn't work

Question

I have this function below, but the if statement inside the for loop doesn't work. I tried <= instead of < and also round(), but they didn't work.

function points1=tracker(count1,points1,u,v,I2)

for j=1:count1

   if  (points1(1,j) < size(u,1))&&(points1(2,j) < size(u,2))

       points1(1,j)= points1(1,j)+v(points1(1,j),points1(2,j));
       points1(2,j)= points1(2,j)+u(points1(1,j),points1(2,j));
       I2(round(points1(1,j)),round(points1(2,j)))=255;

   else

       points1(:,j)=[];
       count1=count1-1;
       j=j-1;

   end

end

    figure, imshow(I2)

end

What exactly doesn't work about it?

tmpearce
– tmpearce

2013-07-29 15:08:02 +00:00
Commented Jul 29, 2013 at 15:08 — tmpearce
– tmpearce, Commented Jul 29, 2013 at 15:08
Did my answer solve your question?

horchler
– horchler

2013-08-02 20:53:45 +00:00
Commented Aug 2, 2013 at 20:53 — horchler
– horchler, Commented Aug 2, 2013 at 20:53

horchler · Accepted Answer · 2013-07-29 15:24:25Z

8

You're trying to change the increment of the for loop, j, from within the loop (your j=j-1 line). You can't do this. The documentation for for states:

Avoid assigning a value to the index variable within the body of a loop. The for statement overrides any changes made to the index within the loop.

You'll need to use a while loop instead or find another way of doing what you need using an intermediate variable.

edited Jul 29, 2013 at 15:24

answered Jul 29, 2013 at 15:14

horchler

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