MATLAB: For loop, exceeded dimension error.

for loopMATLABrow deleting

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.

Best Answer

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

Related Solutions

MATLAB: How to record all cases where two columns sum to a third

A solution that does not involve any loop:

m = [2 0 1 2 1
     1 1 0 0 1];
[col1, col2] = ndgrid(1:size(m, 2));   %cartesian product of column indices
mask = triu(true(size(col1)), 1);      %mask to only keep columns where col2 > col1
col1 = col1(mask);
col2 = col2(mask);
[issum, colsum] = ismember((m(:, col1) + m(:, col2)).', m.', 'rows');  %note the transpose because of the 'rows' option
result = [colsum(issum), col1(issum), col2(issum)].'  %use sortrows before the transpose if the order is important

MATLAB: Improve the code’s time of execution. I want to avoid the for loops and use element by element calculations. Do you guys have something in mind?? Thank you in advance.

See if the following produces correct output, first; should reduce the time slightly by eliminating redundant tests and shortening the loop on j. Whether it's significant will depend how many cases get missed so is data-dependent.

for i=1:v
  for j=1:n
    if j==A, continue, end
    for k=1:n
      if k==dm 
        ddii=((design(i,k)-design(j,k))^2);
        summ=summ+ddii; 
      else
        ddii=((design(A,k)-design(j,k))^2);
        summ=summ+ddii;                                  
      end
    end
    ddcc(j,i,:)=[j i summ];
    summ=0;
  end
  cc(i,:)=min(nonzeros(ddcc(:,i,3))); 
end

After that, you're walking thru the arrays in the opposite storage as to sequential addressing; whether this is a major issue has to do with stride and cache size, etc., but might try using

design=design.';

before beginning the loop and see if it makes any difference in speed when the first index gets incremented sequentially in the innermost loop.

After that, I'd have to think more than I wish to expend on a Sunday afternoon to see if could do better on the actual computation altho it would seem with some consideration a logical addressing expression and pdist|pdist2 should be able to help.

Best Answer

Related Solutions

MATLAB: How to record all cases where two columns sum to a third

MATLAB: Improve the code’s time of execution. I want to avoid the for loops and use element by element calculations. Do you guys have something in mind?? Thank you in advance.

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