Generate a user-defined mediation model

Generates lavaan model syntax for a user-defined within-subject mediation model. Users specify directed paths among mediators and from mediators to the outcome. The function automatically adds the corresponding difference and level components and identifies all indirect effects.

Usage

GenerateModelCustom(prepared_data, paths, MP = character(0))

Arguments

prepared_data

A data frame returned by PrepareData(). It must contain M1diff, M1avg, ..., and Ydiff.

paths

A character vector defining directed paths among mediators and from mediators to the outcome. For example: c("M1 -> M2", "M2 -> Y").

MP

A character vector identifying moderated paths. Supported labels follow the existing wsMed convention: a1, b1, d1, b_1_2, d_1_2, and cp.

Main effects of W are always labeled and used for conditional intercepts, including when a/cp is not explicitly listed in MP.

Value

A character string containing lavaan model syntax.

Product moments

When a moderated path starts at an endogenous mediator, auxiliary product moment equations and covariances with its upstream disturbances preserve the joint predictor moment structure under reference recoding. These equations are not additional mediation paths. Genuine exogenous moments follow the fitting function's fixed.x setting; endogenous product moments are estimated.

Examples

prepared_data <- data.frame(
  M1diff = rnorm(100),
  M1avg  = rnorm(100),
  M2diff = rnorm(100),
  M2avg  = rnorm(100),
  M3diff = rnorm(100),
  M3avg  = rnorm(100),
  Ydiff  = rnorm(100)
)

model <- GenerateModelCustom(
 prepared_data = prepared_data,
 paths = c(
   "M1 -> M3",
   "M1 -> Y",
   "M3 -> Y",
   "M2 -> Y"
 )
)

cat(model)
#> Ydiff ~ cp*1 + b1*M1diff + d1*M1avg + b2*M2diff + d2*M2avg + b3*M3diff + d3*M3avg
#> M1diff ~ a1*1
#> M2diff ~ a2*1
#> M3diff ~ a3*1 + b_1_3*M1diff + d_1_3*M1avg
#> indirect_1_3 := a1 * b_1_3 * b3
#> indirect_1 := a1 * b1
#> indirect_2 := a2 * b2
#> indirect_3 := a3 * b3
#> total_indirect := indirect_1_3 + indirect_1 + indirect_2 + indirect_3
#> total_effect := cp + total_indirect