For loop, exceeded dimension error.

Hi, this is most certainly an easy fix on which I seem to got myself stuck.

The loop should compare elements of an array and if it finds that they are equal it shall erase that row, next it shall recompute the size of the array and redo the comparison for the next element:

for ii=1:N   
   if (ii>1) && (ii<N)
    i3=ii+1;
    for jj=i3:N
         if DD(ii,1)==DD(jj,1)
            DD(jj,:)=[];
            [N,M]=size(DD);
         end
    end
   end
end

I get the following error:

      ??? Index exceeds matrix dimensions.

      Error in ==> VB_CompDin2Darray at 29
               if DD(ii,1)==DD(jj,1)

A pointer would be great. Cheers.

Answer 1

[Sean de Wolski]

Simply run the loop backwards so row 4 doesn't become row 3 when row 3 is deleted.

e.g:

for jj = N:-1:i3
  %delete stuff
end

Now of course you're still best off (for speed) building an index vector and doing the whole delete once at the end.

idx = false(N-i3,1);
for jj = i3:N
 if stuff
    idx(jj) = true;
 end
 Mat(idx,:) = [];
end

[Victor Buza]

Great! Thanks. What was the problem with row 4 becoming 3? I mean, it was still resizing and comparing the element, wasn't it?

[Jan]

@Victor: The loop "for jj=i3:N" runs until the inital value of N, even if N is modified inside the loop. In most other programming languages modifying the limit inside the loop effect the number of iterations.

[Sean de Wolski]

If you delete row 3; what happens to row 4? It becomes row 3! Now your matrix size is smaller, but the for-loop still wants to go to the ORIGINAL N.

[Sean de Wolski]

Use unique, as Jan has suggested, anyway.

Answer 2

[Jan]

Simple and efficient for large matrices:

[dummy, index] = unique(DD(:, 1));
DD = DD(index, :);

[Victor Buza]

Thank you;