First, each node in the network is assigned to its own community.
\Delta Q = \bigg[ \frac{\Sigma_{in} + 2k_{i,in}}{2m} - \bigg(\frac{\Sigma_{tot} + k_i}{2m}\bigg)^2 \bigg]-\bigg[\frac{\Sigma_{in}}{2m} - \bigg(\frac{\Sigma_{tot}}{2m}\bigg)^2-\bigg(\frac{k_i}{2m}\bigg)^2\bigg] .