I am assuming all your data files have the same format. You should convert your current code into a function and call it 3 times with the different filenames. Also do not use global variable to store DATA.
% INPUT_FILES_2.m
function DATA=INPUT_FILES_2(filename)
fid = fopen(filename,'rt');
fgetl(fid);
DATA.data = fscanf(fid,'%f',[7, Inf]);
DATA.data = DATA.data';
DATA.xte = DATA.data(1,2);
DATA.rows_remove = find(DATA.data(:,2)>DATA.xte);
if (~isempty(DATA.rows_remove))
DATA.data = DATA.data(1:DATA.rows_remove(1)-1,:);
end
end
Now you can call this in your workspace or another script / function to load the 3 files or any number of files.
DATA_A1=INPUT_FILES_2('a1.DAT');
DATA_A2=INPUT_FILES_2('a2.DAT');
DATA_A3=INPUT_FILES_2('a3.DAT');
