How to exact first number of values from a variable with changed length in a loop

Hi,

I have a data with three dimensions, the length of third dimension varies. Most of them are 29, but three of them are more than 29.

I want to keep exacting first 29 vectors from this matric, but I have no idea how to achieve it in the loop.

My code is like this:

The epoch_num is the variable with changing length (29 or more than 29) frag_eegs is the variable I need and store my new datasets.

% put your data into these segments       
for epoch_num=1:size(EEG.data,3)
  frag_eegs(:,1,epoch_num)=eeg_data(1:seg_length,epoch_num);
  for n=2:num_seg
    frag_eegs(:,n,epoch_num)=eeg_data(seg_length*(n-1):((seg_length*n)-1),epoch_num);
  end
end

Hope I explain clearly. Thank you!

[dpb]

Nmax=29;        % desired upper limit
for epoch_num=1:min(size(EEG.data,3),Nmax)
  ...