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Transmission mode (push or pull)

Source: R/transmission-mode.R
transmission-mode.Rd

Controls how network models compute transmission each day.

Usage

set_transmission_mode(model, mode = c("auto", "push", "pull"), kappa = NULL)

get_transmission_mode(model)

get_last_transmission_mode(model)

get_transmission_kappa(model)

Arguments

model

An epiworld_model object.

mode

Character scalar. One of "auto", "push", or "pull". "pull" reproduces the random streams of epiworld 0.15 and earlier.

kappa

Numeric scalar. Threshold used by "auto"; a finite, non-negative number. Smaller values pull more often. When NULL, the default of the C++ library is used (0.5).

Value

  • set_transmission_mode() returns the model invisibly.

  • get_transmission_mode() returns "auto", "push", or "pull", as set with set_transmission_mode().

  • get_last_transmission_mode() returns "push" or "pull": the mode used in the most recent step of the last run.

  • get_transmission_kappa() returns the kappa threshold.

Details

In a pull step, each susceptible agent looks at its infected neighbors. In a push step, each infected agent adds its infection odds to its susceptible neighbors. Both give the same distribution of infections; they differ only in speed and in the random numbers drawn, so the same seed gives different (but equally valid) runs under each mode.

Pushing is cheaper while few agents are infected; pulling can be cheaper near the peak of a large outbreak. "auto", the default, chooses each day: it pushes when \(D_c + 4 N_c \le \kappa (D_s + 4 N_s)\), where \(D\) is the sum of the agents' degrees and \(N\) the number of agents, over the infected agents that can transmit (\(c\)) and the susceptible agents (\(s\)), and pulls otherwise.

Only susceptible states that use epiworld's default network sampler can be pushed. Other models, e.g., mixing models (ModelSIRMixing()) and connected models (ModelSIRCONN()), always pull, as do directed networks.

Examples

model <- ModelSIR(
  name = "A Virus", prevalence = .01, transmission_rate = .5,
  recovery_rate = 1/7
)
agents_smallworld(model, n = 10000, k = 5, d = FALSE, p = .01)
verbose_off(model)

get_transmission_mode(model)
#> [1] "auto"
get_transmission_kappa(model)
#> [1] 0.5

# Always push
set_transmission_mode(model, "push")
run(model, ndays = 50, seed = 1912)
get_last_transmission_mode(model)
#> [1] "push"