MATLAB: Is several small functions preferred rather than a few long ones in GUI

MATLABmatlab gui

I know this question has been asked before in different variations, but as a novice I need a bit help with best practice. I have a GUI (see code below) where I use a pushbutton to select a folder containing a lot of *.asc files. All these files are imported through a for loop as a text array inside one large cell array, for instance a 1×10 cell where each cell contain a subarray (30×13 cell). I hope this makes sense? from these cell I extract different variables and do various calculations. Now my question is: Will it be better practice to split large function (here pushbutton1) into minor functions such as one function for folder selection and one function for importing and another function for extracting parameters and yet another function for calculations etc…?
function pushbutton1_Callback(hObject, eventdata, handles)
%%Import every rawdata (*.asc) files from selected folder
Folder='C:\Users\test\GUI1.3\';      %start location for the folder selection
dirname = uigetdir(fullfile(Folder, ''), 'Select a directory');
  if ~ischar(dirname); 
  return; 
  end                                           %user canceled
dinfo = dir( fullfile( dirname, '*.asc') );
files=fullfile( {dirname},{dinfo.name});
numfiles = length(dinfo);  
names = cell(1, numfiles); 
Alldata = cell(1, numfiles);
for k = 1:numfiles  
    % Initialize variables.
    filename = files{1,k};
    delimiter = '\t';
      % Format string for each line of text (column1-13: text (%s)):
      formatSpec = '%s%s%s%s%s%s%s%s%s%s%s%s%s%[^\n\r]';
      % Open the text file.
      fileID = fopen(filename,'r');
      % Read columns of data according to format string.
      dataArray = textscan(fileID, formatSpec, 'Delimiter', delimiter,  'ReturnOnError', false);
      % Close the text file.
      fclose(fileID);
      % Create output variable and insert in the "Alldata" cell array
      Alldata{k}=[dataArray{1:end-1}];
      names{k}=getfield(dinfo(k), 'name');
  end

Best Answer

Splitting large functions is always better practice. A function should have a specific logical role.
That being said, when you have a huge loop it is better to put the whole loop in a function rather than the contents of the loop because function invocation has an overhead.
Then again your mere 10×30 cells will amount to a few milliseconds that no user would notice.
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