lav_constraints: Utility Functions: Constraints

In lavaan: Latent Variable Analysis

Utility Functions: Constraints

Description

Utility functions for equality and inequality constraints.

Usage

lav_con_parse(partable = NULL, constraints = NULL, theta = NULL,
                      debug = FALSE, box_fast = NULL)
lav_pt_con_ceq(partable, con = NULL, debug = FALSE,
                             txt_only = FALSE)
lav_pt_con_ciq(partable, con = NULL, debug = FALSE,
                             txt_only = FALSE)
lav_pt_con_def(partable, con = NULL, debug = FALSE,
                             txt_only = FALSE, warn = TRUE)

Arguments

partable	A lavaan parameter table.
constraints	A character string containing the constraints.
theta	A numeric vector. Optional vector with values for the model parameters in the parameter table.
debug	Logical. If TRUE, show debugging information.
box_fast	Logical. If NULL (default), a fast path is used when the only inequality constraints are finite per-parameter lower/upper bounds (eg the bounds = "standard", "wide" or "pos.var" profiles): the constraint Jacobian is known exactly and is built directly instead of being estimated numerically. If FALSE, the legacy path is always used.
con	An optional partable where the operator is one of ‘==’, ‘>’, ‘<’ or ‘:=’
txt_only	Logical. If TRUE, only the body of the function is returned as a character string. If FALSE, a function is returned.
warn	Logical. If FALSE, warnings are suppressed.

Details

This is a collection of lower-level constraint-related functions that are used in the lavaan code. They are made public at the request of package developers. Below is a brief description of what they do:

The lav_con_parse function parses the constraints specification (provided as a string, see example), and generates a list with useful information about the constraints.

The lav_pt_con_ceq function creates a function which takes the (unconstrained) parameter vector as input, and returns the slack values for each equality constraint. If the equality constraints hold perfectly, this function returns zeroes.

The lav_pt_con_ciq function creates a function which takes the (unconstrained) parameter vector as input, and returns the slack values for each inequality constraint.

The lav_pt_con_def function creates a function which takes the (unconstrained) parameter vector as input, and returns the computed values of the defined parameters.

Examples

myModel <- 'x1 ~ a*x2 + b*x3 + c*x4'
myParTable <- lavParTable(myModel, as_data_frame = FALSE)
con <- ' a == 2*b
         b - c == 5 '
conInfo <- lav_con_parse(myParTable, constraints = con)

myModel2 <- 'x1 ~ a*x2 + b*x3 + c*x4
             a == 2*b
             b - c == 5 '
ceq <- lav_pt_con_ceq(partable = lavParTable(myModel2))
ceq( c(2,3,4) )

lavaan documentation built on Oct. 8, 2026, 5:06 p.m.