Estimate formulas for (co-)variance paths using Wright's path tracing rules

This function estimates the path from x to y using the path tracing rules. Note that it only works with structural parameters, so "=~" are ignored, unless measurement.model = TRUE. If you want to use the measurement model, "~" should be in the mod column of pt.

Usage

trace_path(
  pt,
  x,
  y,
  parenthesis = TRUE,
  missing.cov = FALSE,
  measurement.model = FALSE,
  maxlen = 100,
  ...
)

Arguments

pt: A data frame with columns lhs, op, rhs, and mod, from modsemify
x: Source variable
y: Destination variable
parenthesis: If TRUE, the output will be enclosed in parenthesis
missing.cov: If TRUE, covariances missing from the model syntax will be added
measurement.model: If TRUE, the function will use the measurement model
maxlen: Maximum length of a path before aborting
...: Additional arguments passed to trace_path

Value

A string with the estimated path (simplified if possible)

Examples

library(modsem)
m1 <- '
  # Outer Model
  X =~ x1 + x2 +x3
  Y =~ y1 + y2 + y3
  Z =~ z1 + z2 + z3

  # Inner model
  Y ~ X + Z + X:Z
'
pt <- modsemify(m1)
trace_path(pt, x = "Y", y = "Y", missing.cov = TRUE) # variance of Y
#> [1] "(X~~X * Y~X ^ 2 + 2 * X~~Z * Y~X * Y~Z + Y~Z ^ 2 * Z~~Z + Y~~Y)"