data = xlsread('tjet.xls');   % read in Excel file
U_vec = data(:,2);   % extract velocity vector
u_vec = U_vec - mean(U_vec);   % obtain velocity fluctuation
n = length(u_vec);
for i = 1:n   % loop to sum u_vec entries
    sum = sum + u_vec(i);
    turbInt = (sum^2 / n)^0.5;   %turbulence intensity
end