# VarCorr: Extract variance and correlation components In nlme: Linear and Nonlinear Mixed Effects Models

 VarCorr R Documentation

## Extract variance and correlation components

### Description

This function calculates the estimated variances, standard deviations, and correlations between the random-effects terms in a linear mixed-effects model, of class `"lme"`, or a nonlinear mixed-effects model, of class `"nlme"`. The within-group error variance and standard deviation are also calculated.

### Usage

```VarCorr(x, sigma = 1, ...)
## S3 method for class 'lme'
VarCorr(x, sigma = x\$sigma, rdig = 3, ...)

## S3 method for class 'pdMat'
VarCorr(x, sigma = 1, rdig = 3, ...)
## S3 method for class 'pdBlocked'
VarCorr(x, sigma = 1, rdig = 3, ...)
```

### Arguments

 `x` a fitted model object, usually an object inheriting from class `"lme"`. `sigma` an optional numeric value used as a multiplier for the standard deviations. The default is `x\$sigma` or `1` depending on `class(x)`. `rdig` an optional integer value specifying the number of digits used to represent correlation estimates. Default is `3`. `...` further optional arguments passed to other methods (none for the methods documented here).

### Value

a matrix with the estimated variances, standard deviations, and correlations for the random effects. The first two columns, named `Variance` and `StdDev`, give, respectively, the variance and the standard deviations. If there are correlation components in the random effects model, the third column, named `Corr`, and the remaining unnamed columns give the estimated correlations among random effects within the same level of grouping. The within-group error variance and standard deviation are included as the last row in the matrix.

### Author(s)

José Pinheiro and Douglas Bates bates@stat.wisc.edu

### References

Pinheiro, J.C., and Bates, D.M. (2000) Mixed-Effects Models in S and S-PLUS, Springer, esp. pp. 100, 461.

`lme`, `nlme`
```fm1 <- lme(distance ~ age, data = Orthodont, random = ~age)