This is how I would do it:
for k1 = 1:n
matrix(:,k1) = [k1; a(k1); b(k1); Rsquared_eff(k1); z(k1); t(k1); Rsquared_tox(k1)];
end
I changed the loop counter to ‘k1’ because MATLAB uses i and j for its imaginary operators. Using them as loop counters can create confusion.