modelbpp (version 0.2.0)

get_drop: Models That Are More Restricted

Description

Generate a list of models with one or more free parameter dropped (fixed to zero).

Usage

get_drop(
  sem_out,
  must_drop = NULL,
  must_not_drop = NULL,
  loadings_to_exclude = c("single", "none", "all"),
  df_change = 1,
  model_id = NA,
  keep_correct_df_change = TRUE,
  remove_duplicated = TRUE,
  progress = FALSE
)

Value

An object of the class partables, a named list of parameter tables, each of them to be used by lavaan::lavaan() or update()

for fitting a model with the added parameters.

Arguments

sem_out

The original model, which is the output from an structural equation modeling function. Currently support lavaan::lavaan objects only.

must_drop

A character vector of parameters, named in lavaan::lavaan() style (e.g., "y ~ x"), that must be included. Default is NULL.

must_not_drop

A character vector of parameters, named in lavaan::lavaan() style (e.g., "x1 ~~ x1"), that must not be included. Default is NULL.

loadings_to_exclude

Whether factor loadings will be excluded. If "single", then only "single" loadings (an indicator loads on only one latent factor) will be excluded. If "all", then all factor loadings will be excluded. If "none", then no loadings will be excluded. Be careful when using "none" because the models may not make sense. The settings in must_drop and must_not_drop will override this argument.

df_change

How many degrees of freedom away in the list. All models with df change less than or equal to this number will be included, taking into account requirements set by other arguments. Default is 1.

model_id

The identification number of the starting model. Default is NA, no identification number.

keep_correct_df_change

Keep only models with actual df change equal to expected df change.

remove_duplicated

If TRUE, the default, duplicated models are removed.

progress

Whether a progress bar will be displayed, implemented by the pbapply package. Default is FALSE.

Author

Shu Fai Cheung https://orcid.org/0000-0002-9871-9448

Details

It generates a list of models with one or more free parameters dropped, that is, fixed to zero (with degrees of freedom, df, increases by one or more).

All free parameters are included in the pool of candidates, except for those explicitly requested to be kept.

The models will be checked by lavaan to make sure that the increase in model degrees of freedom is of the expected value.

This function is called by model_set() and usually users do not need to call it. It is exported for advanced users.

See Also

print.partables()

Examples

library(lavaan)

dat <- dat_path_model
mod <-
"
x3 ~ a*x1 + b*x2
x4 ~ a*x1 + x2
ab := a*b
"

fit <- sem(mod, dat_path_model, fixed.x = TRUE)
mod_to_drop <- get_drop(fit)
mod_to_drop