Metallicity–R_b relation for stars in the LMC simulation during interaction phase between the LMC and SMC (1.5–2 Gyr; left), isolation phase (5–5.5 Gyr; middle), and settling phase (6.5–7 Gyr; right). The solid lines show the true metallicity gradient, and the dashed line shows the inference from Range[Fe/H]. The linear relation does fit the outer galaxy well, as the Metallicity–R_b relations are not exactly linear, especially in the inner galaxy. This causes the bias for inferring R_b for the outer galaxy (see Figure 2).