How to change loop condition in Matlab?

Question

I run this code:

for i=1:length(matr)

...where matr is square matrix. In this loop the size of the matr changes, but it seems that the loop continues to run, until i doesn't not exceed the initial value of length(matr)

How to maintain the fresh of length(matr) in the loop's condition?

Here is my code.

for i=1:length(matr1)
       for j=1:length(matr1) 
           if((i~=j)&&(ismember(i,ind3)==0)&&(ismember(j,ind3)==0))
               if (i>length(matr1))||(j>length(matr1))
                   continue
               end
               ind1 = find_tree(matr1,i);
               ind2 = find_tree(matr1,j);
               b = is_isomorphic(matr1(ind1,ind1),matr1(ind2,ind2),encode(ind1),encode(ind2));
               if b,
                   number = number + length(ind1);
                   matr1(ind2,:) = [];
                   matr1(:,ind2) = [];
                   ind3 = find(summ_rows==-1);
               end
           end
       end
    end

I was managed to add

`if (i>length(matr1))||(j>length(matr1))`,

...because i and j exceeded the dimensions of the matrix.

Can you describe what your loop is trying to do? You probably should be using a while loop for this and not a for loop — Dan
– Dan, Commented Mar 11, 2014 at 10:28

Dan · Accepted Answer · 2014-03-11 10:30:08Z

6

You should be using a while loop:

ii = 0;
while(ii <= length(matr))
    ii = ii + 1;

    %// Your loop code here: e.g. the following line that alters the size of matr
    matr = rand(randi(20) + 10);

end

answered Mar 11, 2014 at 10:30

Dan

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4 Comments

Macaronnos Over a year ago

Thank you. And, is it true, that bounds for a for-loop is calculated only before the initial iteration?

Dan Over a year ago

@restrest yes that is true as far as I know. Easy for you to test though

bdecaf Over a year ago

I think this might be related to the JIT acceleration. Could be you get different results once you disable it.

Dan Over a year ago

@bdecaf I haven't tested it but I wouldn't think so. 1:length(matr1) creates a vector [1,2,3... first and then i will iterate over that. I'm pretty confident that this is set when you create the loop and does not change, JIT or no.

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