R: Adjusted denomintor degress freedom for linear estimate for...
get_Lb_ddf
R Documentation
Adjusted denomintor degress freedom for linear estimate for linear
mixed model.
Description
Get adjusted denomintor degress freedom for testing Lb=0 in a
linear mixed model where L is a restriction matrix.
Usage
get_Lb_ddf(object, L)
Lb_ddf(L, V0, Vadj)
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)
V0, Vadj
Unadjusted and adjusted covariance matrix for the fixed effects
parameters. Undjusted covariance matrix is obtained with
vcov() and adjusted with vcovAdj().
Value
Adjusted degrees of freedom (adjusment made by a Kenward-Roger
approximation).
Ulrich Halekoh, S<c3><b8>ren H<c3><b8>jsgaard (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., http://www.jstatsoft.org/v59/i09/
(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<-model2restrictionMatrix(fmLarge, fmSmall)
L