Extract (or "get") components from a KRmodcomp or SATmodcomp object.

Extract (or "get") components from a KRmodcomp or SATmodcomp object. In particular, get denominator degrees of freedom.

getKR(
  object,
  name = c("ndf", "ddf", "Fstat", "p.value", "F.scaling", "FstatU", "p.valueU", "aux")
)

getSAT(object, name = c("ndf", "ddf", "Fstat", "p.value"))

Arguments

object

A KRmodcomp object, which is the result of the KRmodcomp function

name

The available slots. If name is missing or NULL then everything is returned.

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/

Author

Søren Højsgaard sorenh@math.aau.dk

Examples


(fm0 <- lmer(Reaction ~ (Days|Subject), sleepstudy))
#> Linear mixed model fit by REML ['lmerMod']
#> Formula: Reaction ~ (Days | Subject)
#>    Data: sleepstudy
#> REML criterion at convergence: 1769.845
#> Random effects:
#>  Groups   Name        Std.Dev. Corr 
#>  Subject  (Intercept) 25.53         
#>           Days        11.93    -0.18
#>  Residual             25.59         
#> Number of obs: 180, groups:  Subject, 18
#> Fixed Effects:
#> (Intercept)  
#>       257.8  
(fm1 <- lmer(Reaction ~ Days + (Days|Subject), sleepstudy))
#> Linear mixed model fit by REML ['lmerMod']
#> Formula: Reaction ~ Days + (Days | Subject)
#>    Data: sleepstudy
#> REML criterion at convergence: 1743.628
#> Random effects:
#>  Groups   Name        Std.Dev. Corr
#>  Subject  (Intercept) 24.741       
#>           Days         5.922   0.07
#>  Residual             25.592       
#> Number of obs: 180, groups:  Subject, 18
#> Fixed Effects:
#> (Intercept)         Days  
#>      251.41        10.47  
(fm2 <- lmer(Reaction ~ Days + I(Days^2) + (Days|Subject), sleepstudy))
#> Linear mixed model fit by REML ['lmerMod']
#> Formula: Reaction ~ Days + I(Days^2) + (Days | Subject)
#>    Data: sleepstudy
#> REML criterion at convergence: 1742.816
#> Random effects:
#>  Groups   Name        Std.Dev. Corr
#>  Subject  (Intercept) 24.761       
#>           Days         5.925   0.06
#>  Residual             25.534       
#> Number of obs: 180, groups:  Subject, 18
#> Fixed Effects:
#> (Intercept)         Days    I(Days^2)  
#>     255.449        7.434        0.337  

x10 <- KRmodcomp(fm1, fm0)
getKR(x10, "ddf")
#> [1] 17

KRmodcomp(fm1, fm0) |> getKR("ddf")
#> [1] 17
KRmodcomp(fm2, fm0) |> getKR("ddf")
#> [1] 39.81704
KRmodcomp(fm2, fm1) |> getKR("ddf")
#> [1] 143

## For comparison:

SATmodcomp(fm1, fm0) |> getSAT("ddf")
#> [1] 16.99998
SATmodcomp(fm2, fm0) |> getSAT("ddf")
#> [1] 51.56303
SATmodcomp(fm2, fm1) |> getSAT("ddf")
#> [1] 143.0001