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Update the initial compartment state (u0) in each node

Source: R/u0.R
u0-set.Rd

Replace the initial state vector (u0) of a SimInf_model object with new data. This allows you to modify the starting conditions of a model without recreating the object.

Usage

u0(model) <- value

# S4 method for class 'SimInf_model'
u0(model) <- value

Arguments

model

A SimInf_model object.

value

An object containing the new initial state. Can be a data.frame, matrix, or named numeric vector. Non-data.frame inputs will be coerced to a data.frame.

Value

The modified SimInf_model object.

Details

The value argument accepts a data.frame, matrix, or named numeric vector. If the input is not a data.frame, it will be automatically coerced to one. The function handles the following formats:

  • Single Node: If value is a named vector or a one-row matrix/data.frame, it is applied to the single node in the model.

  • Multiple Nodes: If value is a matrix or data.frame with multiple rows, each row corresponds to one node. The number of rows must exactly match the number of nodes in the model.

  • Column Matching: Column names must match the compartment names defined in the model (e.g., "S", "I", "R"). Only matching columns are used; extra columns are ignored, and missing compartments will trigger an error.

The function validates the input and ensures the new state is consistent with the model structure before updating.

See also

v0<- for updating the initial continuous state.

Examples

## For reproducibility, set the seed.
set.seed(22)

## Create a single-node SIR model.
model <- SIR(
  u0 = data.frame(
    S = 99,
    I = 1,
    R = 0
  ),
  tspan = 1:100,
  beta = 0.16,
  gamma = 0.077
)

## Update u0 using a named vector (automatically coerced to one
## row).
u0(model) <- c(
  S = 990,
  I = 10,
  R = 0
)

result <- run(model)
plot(result)


## Create a multi-node model (2 nodes).
model_multi <- SIR(
  u0 = data.frame(
    S = c(100, 50),
    I = c(1, 0),
    R = c(0, 0)
  ),
  tspan = 1:100,
  beta = 0.16,
  gamma = 0.077
)

## Update u0 using a data.frame with multiple rows.
u0(model_multi) <- data.frame(
  S = c(200, 100),
  I = c(5, 2),
  R = c(0, 0)
)

result <- run(model_multi)
plot(result)