R: Approximate stratum variances

asv.asreml {asreml} | R Documentation

## Approximate stratum variances

### Description

Generic function to compute approximate stratum variances, degrees of freedom and coefficients for variance component models.

### Usage

    ## S3 method for class 'asreml'
    asv(object, order = c("as.is", "noeff"), vvp = FALSE, ...)

### Arguments

`object` | An object of class `asreml`.
`order` | The sequence in which to consider the random terms. Options are `"as.is"` for the order as given in the `asreml` object, or `"noeff"` to be ordered by increasing number of effects, respectively. Note that the default ordering for random terms in `asreml` is `"noeff"` (default = `"as.is"`).
`vvp` | If `TRUE`, the inverse of the average information matrix for the variance components (sigma scale) is returned (default = `FALSE`).
`...` | Any additional arguments.

### Details

For linear mixed effects model, it is often possible to consider a natural ordering of the variance component parameters, including the residual. Based on an idea due to Thompson, 1980; here, `asreml` computes approximate stratum degrees of freedom and stratum variances by a modified Cholesky diagonalisation of the average information matrix.

### Value

If `vvp = FALSE`, a rectangular matrix containing the degrees of freedom, approximate variances and the component coefficients for each random term is provided.

If `vvp = TRUE`, a list of length two containing the matrix of approximate stratum variances and the inverse average information matrix of the variance components in list components `asv` and `vvp`, respectively, is provided.

[Package asreml version 4.2.0.480 Index]