get_ddf_Lb: Adjusted denominator degrees of freedom for linear estimate...

In pbkrtest: Parametric Bootstrap, Kenward-Roger and Satterthwaite Based Methods for Test in Mixed Models

Adjusted denominator degrees of freedom for linear estimate for linear mixed model.

Description

Get adjusted denominator degrees freedom for testing Lb=0 in a linear mixed model where L is a restriction matrix.

Usage

get_Lb_ddf(object, L)

## S3 method for class 'lmerMod'
get_Lb_ddf(object, L)

get_ddf_Lb(object, Lcoef)

## S3 method for class 'lmerMod'
get_ddf_Lb(object, Lcoef)

Lb_ddf(L, V0, Vadj)

ddf_Lb(VVa, Lcoef, VV0 = VVa)

Arguments

object	A linear mixed model object.
L	A vector with the same length as fixef(object) or a matrix with the same number of columns as the length of fixef(object)
Lcoef	Linear contrast matrix
V0, Vadj	The unadjusted and the adjusted covariance matrices for the fixed effects parameters. The unadjusted covariance matrix is obtained with vcov() and adjusted with vcovAdj().
VVa	Adjusted covariance matrix
VV0	Unadjusted covariance matrix

Value

Adjusted degrees of freedom (adjustment made by a Kenward-Roger approximation).

Author(s)

Søren Højsgaard, [e-mail]

References

Ulrich Halekoh, Søren Højsgaard (2014)., A Kenward-Roger Approximation and Parametric Bootstrap Methods for Tests in Linear Mixed Models - The R Package pbkrtest., Journal of Statistical Software, 58(10), 1-30., https://www.jstatsoft.org/v59/i09/

See Also

KRmodcomp, vcovAdj, model2restriction_matrix, restriction_matrix2model

Examples

(fmLarge <- lmer(Reaction ~ Days + (Days|Subject), sleepstudy))
## removing Days
(fmSmall <- lmer(Reaction ~ 1 + (Days|Subject), sleepstudy))
anova(fmLarge, fmSmall)

KRmodcomp(fmLarge, fmSmall)  ## 17 denominator df's
get_Lb_ddf(fmLarge, c(0, 1)) ## 17 denominator df's

# Notice: The restriction matrix L corresponding to the test above
# can be found with
L <- model2restriction_matrix(fmLarge, fmSmall)
L

pbkrtest documentation built on June 27, 2024, 1:07 a.m.