In our experimental setting, we can construct a natural Twitter network summarized by the network schema in Figure 3.
the above optimization problem can be solved directly since Q(Y) is convex (Zhu et al., 2003;Zhou et al., 2004  a closed form solution can be derived as Y * u = (D uu + µI uu − W uu ) −1 (W ul Y l + µY 0 u ).