asv.asreml {asreml} | R Documentation

## Approximate stratum variances.

### Description

Function to compute the approximate stratum variances, degrees of freedom and coefficients for simple 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: may be one of `"as.is"` or `"noeff"` for the order as given in the `asreml` object, or ordered by increasing number of effects, respectively. The default is `"as.is"`. Note that the default ordering for random terms in `asreml` is `"noeff"`.
`vvp` | If `TRUE` (the default is `FALSE`) the inverse of the average information matrix for the variance components (sigma scale) is returned.
`...` | Any additional arguments.

### Details

Approximate stratum variances and degrees of freedom for simple variance components models are returned. For the 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, `asreml` computes approximate stratum degrees of freedom and stratum variances by a modified Cholesky diagonalisation of the average information matrix.

### Value

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

### References

Thompson R (1980). “Maximum likelihood estimation of variance components.” Series Statistics, 11(4), 545–561.

[Package asreml version 4.1.0.176 Index]