The number of nodes with inward external transfer events to each node.
Examples
## Create an 'SIR' model with 1600 nodes and initialize
## it with example data.
model <- SIR(u0 = u0_SIR(), tspan = 1:1460, events = events_SIR(),
beta = 0.16, gamma = 0.077)
## Display indegree for each node in the model.
plot(indegree(model))