How to define starting state of queueing model in r simmer?

Question

Here's the standard bank counter problem to illustrate my question:

Consider a simple bank with customers arriving at random. Customers are to be served at one of two counters, taking a random time for service at each. Also, assume that waiting customers form a single FIFO queue.

Here's the complication:

Suppose we are interested in modeling this system starting noon of a particular day instead of at the start of the day. At noon, both counters are occupied and there is already a queue of 4 customers.

Is there a way to build in this starting state in R simmer?

Here's the code I already have:

library(simmer)

set.seed(1234)

customer <- 
  trajectory("Customer's path") %>%
  log_("Here I am") %>% 
  set_attribute("start_time", function() {now(bank)}) %>% 
  seize("counter") %>% 
  log_(function() {paste("Waited: ", now(bank) - get_attribute(bank, "start_time"))}) %>% 
  timeout(function() {rexp(1, 1/12)}) %>% 
  release("counter") %>% 
  log_(function() {paste("Finished: ", now(bank))})

bank <- 
  simmer("bank") %>% 
  add_resource("counter", 2) %>% 
  add_generator("Customer", customer, function() sample(1:15,1))

bank %>% run(until = 300)

Answer 1

You can set the initial conditions pretty easily: just add another generator to put 6 arrivals at t=0. And if you need to further customise their service times, set up another trajectory for that purpose.