Compare Two Models

Helper functions to compare two models (parameter tables) and find the differences.

Usage

model_diff(
  model_x,
  model_y,
  cols = getOption("semeqmodels.digest_cols", default = c("lhs", "op", "rhs", "block",
    "group", "free", "ustart", "start")),
  digits = 6,
  model_x_name = NULL,
  model_y_name = NULL
)

model_diff_many(
  target_model,
  other_models,
  ...,
  target_model_name = NULL,
  other_models_names = NULL
)

# S3 method for class 'model_diff'
print(x, format = c("summary", "data.frame"), ...)

# S3 method for class 'model_diff_many'
print(x, format = "summary", ...)

Arguments

model_x, model_y

Models as parameter tables (the output lavaan::parameterTable) to be compared. They can also be lavaan objects, the output of functions such as lavaan::sem().

cols

The columns to be compared. Two parameters are considered to be identical if they are identical on these columns (but see Details on how free, ustart, and start are compared).

digits

The number of decimal places used to round ustart and start when doing the comparison.

model_x_name, model_y_name

The names of the models used in the output. If NULL, the name will be generated automatically.

target_model

A model (lavaan parameter table or lavaan output) which other models will be compared with.

other_models

A list of models (lavaan parameter tables or lavaan outputs) to be compared to the target_model by model_diff().

...

For model_diff_many(), these are arguments to be passed to model_diff(). For the print-methods, these arguments are ignored.

target_model_name, other_models_names

Names of the models to be passed to model_diff(). If NULL, they will be generated automatically.

x

The object to be printed.

format

The format of the output when printing model differences. Either a user-friendly summary ("summary") or the original parameter table ("data.frame").

Value

The function model_diff() returns a list with two elements, model_x_only and model_y_only. Each element is a parameter table with parameters that are present only in one of the models. If there is no parameter that is present only in a model, then the element is still a parameter table, though with zero row. The list is of the class model_diff, with a print method.

The function model_diff_many() returns a list of the results of model_diff(). The list is of the class model_diff_many, with a print method.

The print-method of the output of model_diff() returns x invisibly. It is called for its side effect.

The print-method of the output of model_diff_many() returns x invisibly. It is called for its side effect.

Details

model_diff()

The functions model_diff() takes two models (parameter tables) and identifies their differences, if any.

The columns compared are specified by the argument cols.

For the free column, the actual values are ignored. Two parameters are considered identical if they are both free (have non-zero values on free).

For the ustart and start columns, the values are used only if a parameter is fixed. If a parameter is free, they will be recoded to NA when being compared.

model_diff_many()

The function model_diff_many() compares one model (target_model) against several other models (other_models) using model_diff().

The print method of the output of model_diff()

The print method of the output of model_diff() prints the differences between models in a user-friendly way.

The print method of the output of model_diff_many()

The print method of the output of model_diff_many() prints the list of model differences in a user-friendly way.

Examples

library(lavaan)


mod1 <-
"
m ~ x
y ~ m + x
"

mod2 <-
"
m ~ x
y ~ m
"

mod3 <-
"
y ~ m + x
"

pt1 <- parameterTable(sem(mod1, do.fit = FALSE))
pt2 <- parameterTable(sem(mod2, do.fit = FALSE))
pt3 <- parameterTable(sem(mod3, do.fit = FALSE))

model_diff(pt1, pt2)
#> 
#> Model: pt1
#> y~x (free)
#> 
#> Model: pt2
#> No parameter only in this model.
model_diff(pt1, pt3)
#> 
#> Model: pt1
#> m~x (free)
#> m~~m (free)
#> 
#> Model: pt3
#> m~~m (fixed to 1)
#> m~~x (fixed to 0)
model_diff(pt2, pt3)
#> 
#> Model: pt2
#> m~x (free)
#> m~~m (free)
#> 
#> Model: pt3
#> y~x (free)
#> m~~m (fixed to 1)
#> m~~x (fixed to 0)