expand.model.frame {stats} | R Documentation |

## Add new variables to a model frame

### Description

Evaluates new variables as if they had been part of the formula of the
specified model. This ensures that the same `na.action`

and
`subset`

arguments are applied and allows, for example, `x`

to be recovered for a model using `sin(x)`

as a predictor.

### Usage

expand.model.frame(model, extras,
envir = environment(formula(model)),
na.expand = FALSE)

### Arguments

`model` |
a fitted model |

`extras` |
one-sided formula or vector of character strings
describing new variables to be added |

`envir` |
an environment to evaluate things in |

`na.expand` |
logical; see below |

### Details

If `na.expand=FALSE`

then `NA`

values in the extra variables
will be passed to the `na.action`

function used in
`model`

. This may result in a shorter data frame (with
`na.omit`

) or an error (with `na.fail`

). If
`na.expand=TRUE`

the returned data frame will have precisely the
same rows as `model.frame(model)`

, but the columns corresponding to
the extra variables may contain `NA`

.

### Value

A data frame.

### See Also

`model.frame`

,`predict`

### Examples

model <- lm(log(Volume) ~ log(Girth) + log(Height), data=trees)
expand.model.frame(model, ~ Girth) # prints data.frame like
dd <- data.frame(x=1:5, y=rnorm(5), z=c(1,2,NA,4,5))
model <- glm(y ~ x, data=dd, subset=1:4, na.action=na.omit)
expand.model.frame(model, "z", na.expand=FALSE) # = default
expand.model.frame(model, "z", na.expand=TRUE)

[Package

*stats* version 2.2.1

Index]