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3. asv.asreml – Approximate stratum variances

# asv.asreml – Approximate stratum variances

###### Description

asv.asreml computes 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), pp. 545-561.

Updated on August 7, 2018