Description Usage Arguments Details Value Author(s) References See Also Examples

View source: R/influence_functions.R

This function calculates the leverage of
a hierarchical linear model fit by `lmer`

.

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`object` |
fitted object of class |

`...` |
do not use |

`level` |
the level at which the leverage should be calculated: either
1 for observation level leverage (default) or the name of the grouping factor
(as defined in |

Demidenko and Stukel (2005) describe leverage for mixed (hierarchical)
linear models as being the sum of two components, a leverage associated with the
fixed (*H_1*) and a leverage associated with the random effects (*H_2*) where

*H_1 = X (X^\prime V^{-1} X)^{-1} X^\prime V^{-1}*

and

*H_2 = ZDZ^{\prime} V^{-1} (I - H_1)*

Nobre and Singer (2011) propose using

*H_2^* = ZDZ^{\prime}*

as the random effects leverage as it does not rely on the fixed effects.

For individual observations `leverage`

uses the diagonal elements of the
above matrices as the measure of leverage. For higher-level units,
`leverage`

uses the mean trace of the above matrices associated with each
higher-level unit.

`leverage`

returns a data frame with the following columns:

`overall`

The overall leverage, i.e.

*H = H_1 + H_2*.`fixef`

The leverage corresponding to the fixed effects.

`ranef`

The leverage corresponding to the random effects proposed by Demidenko and Stukel (2005).

`ranef.uc`

The (unconfounded) leverage corresponding to the random effects proposed by Nobre and Singer (2011).

Adam Loy loyad01@gmail.com

Demidenko, E., & Stukel, T. A. (2005)
Influence analysis for linear mixed-effects models.
*Statistics in Medicine*, **24**(6), 893–909.

Nobre, J. S., & Singer, J. M. (2011)
Leverage analysis for linear mixed models.
*Journal of Applied Statistics*, **38**(5), 1063–1072.

`cooks.distance.mer`

, `mdffits.mer`

,
`covratio.mer`

, `covtrace.mer`

, `rvc.mer`

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```
Attaching package: ‘HLMdiag’
The following object is masked from ‘package:stats’:
covratio
overall fixef ranef ranef.uc
1 0.22930404 0.019191919 0.21011212 0.9345897
2 0.16972999 0.013804714 0.15592528 1.0174683
3 0.12682372 0.009764310 0.11705941 1.2074459
4 0.10058520 0.007070707 0.09351449 1.5045226
5 0.09101445 0.005723906 0.08529055 1.9086983
6 0.09811147 0.005723906 0.09238756 2.4199730
overall fixef ranef ranef.uc
1 0.161234 0.01111111 0.1501229 2.592732
2 0.161234 0.01111111 0.1501229 2.592732
3 0.161234 0.01111111 0.1501229 2.592732
4 0.161234 0.01111111 0.1501229 2.592732
5 0.161234 0.01111111 0.1501229 2.592732
6 0.161234 0.01111111 0.1501229 2.592732
```

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