Phase plot S vs I

Draws a trajectory in the \((S, I)\) plane. Useful for visualising the epidemic orbit and threshold behaviour.

Usage

plot_phase_si(df)

Arguments

df

A data frame with columns time, S, and I.

Value

A ggplot object.

Examples

sir = model_sir(
  init   = c(S = 990, I = 10),
  params = c(beta = 0.002, gamma = 0.1),
  times  = seq(0, 50, by = 0.1)
)
plot_phase_si(sir)