# Modifying model parameters.

### Description

These functions can be used to change the size of a model's fixed effects, its random effect variance/covariance matrices, or its residual variance. This gives you more control over simulations from the model.

### Usage

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### Arguments

`object` |
a fitted model object. |

`value` |
new parameter values. |

### Details

New values for `VarCorr`

are interpreted as variances and covariances, not standard deviations and
correlations. New values for `sigma`

and `scale`

are interpreted on the standard deviation scale.
This means that both `VarCorr(object)<-VarCorr(object)`

and `sigma(object)<-sigma(object)`

leave `object`

unchanged, as you would expect.

`sigma<-`

will only change the residual standard deviation,
whereas `scale<-`

will affect both `sigma`

and `VarCorr`

.

These function can be used to change the value of individual parameters, such as a single fixed effect coefficient, using standard R subsetting commands.

### See Also

`getData`

if you want to modify the model's data.

### Examples

1 2 3 4 | ```
fm <- lmer(y ~ x + (1|g), data=simdata)
fixef(fm)
fixef(fm)["x"] <- -0.1
fixef(fm)
``` |