y = [0.228 0.189 0.127 8.28e-2 4.93e-2 -9.757e-3 -6.161e-2 -0.108 -0.143 -0.211];
t = [30.705 30.739 30.775 30.808 30.841 30.875 30.908 30.941 30.975 31.008];
p = polyfit(t, y, 1)