Determine which agents changed states
state_change_inds(new_states, current_states, type = "inf")
| new_states | vector of size n_agents of 0/1/2 |
|---|---|
| current_states | vector of size n_agents of 0/1/2 |
| type | either "inf" for new infectious or "rec" for new recovered |
indices of which agents who were in state type are now in the next state