kk1991 - if you only want to read the first line in the file, then don't use the while loop or use break to exit the loop once the first line has been read. Or do you mean something else by I want the script to only read the firs line/row in the text file.
For example, your code could become just
tmp = textscan(tline, '%s ', 'delimiter', ' ', 'MultipleDelimsAsOne', 1);
tmp = tmp{1};
t = str2num(tmp{1});
x = str2num(tmp{2});
where you initialize tline as before.
