How to deal with the problem of the changing size data?

I have the following code:

im = {};
k = 0
while not_end():
  im = {im{:}, dir(filepath, fileArray(k))};
  k = k + 1;
end

where we assume that the fileArray is too big so I cannot pre-allocate im using length(fileArray). Moreover, you cannot also predict when not_end() becomes false. The example itself is artificial, the point is I cannot pre-allocate the cell array im for some reasons. Is there any structure in Matlab that can be used to add elements (like linked list for example) to the structure itself without much loss of the performance?

[Oleg Komarov]

Saying you cannot preallocate im because length(fileArray) is too big doesn't make sense unless it's length is infinite.

Answer 1

[Oleg Komarov]

What is fileArray?

You can always preallocate im as a cell array with length equal to fileArray and extract/concatenate once the loop is finished.

for k = 1:length(fileArray)
    im{k} = dir(filepath, fileArray(k));
end

im = cat(1,im{:});

EDIT

You cannot do otherwise (still the concatenation is better done once and outside of the cycle):

k = 0;
while...
    k = k + 1;
    im{k} = dir(filepath, fileArray(k));
end
im = cat(1,im{:});

[Mateusz]

Well, I cannot predict the size of the cell array. I think my example was misleading, I will re-edit it now.

[Walter Roberson]

You didn't increment k, Oleg.

[Oleg Komarov]

Thanks for pointing that out.