The degree matrix $D$ of a similarity graph is a diagonal matrix where its diagonal elements are $d_{i,i} = \sum_j w_{i,j}$ and its off-diagonal elements are $d_{i,k} = 0$ for $k \neq i$. Here, $w_{i,j}$ are the elements of the weighted adjacency matrix $W$, and $d_{i,k}$ are the elements of $D$.