# varFixed

##### Fixed Variance Function

This function is a constructor for the `varFixed`

class,
representing a variance function with fixed variances. Letting \(v\)
denote the variance covariate defined in `value`

, the variance
function \(\sigma^2(v)\) for this class is
\(\sigma^2(v)=|v|\). The variance covariate \(v\) is
evaluated once at initialization and remains fixed thereafter. No
coefficients are required to represent this variance function.

- Keywords
- models

##### Usage

`varFixed(value)`

##### Arguments

- value
a one-sided formula of the form

`~ v`

specifying a variance covariate`v`

. Grouping factors are ignored.

##### Value

a `varFixed`

object representing a fixed variance function
structure, also inheriting from class `varFunc`

.

##### References

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

##### See Also

##### Examples

```
# NOT RUN {
vf1 <- varFixed(~age)
# }
```

*Documentation reproduced from package nlme, version 3.1-145, License: GPL (>= 2) | file LICENCE*

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