terms.formula {stats} | R Documentation |

## Construct a terms Object from a Formula

### Description

This function takes a formula and some optional arguments and
constructs a terms object. The terms object can then be used to
construct a `model.matrix`

.

### Usage

## S3 method for class 'formula':
terms(x, specials = NULL, abb = NULL, data = NULL, neg.out = TRUE,
keep.order = FALSE, simplify = FALSE, ..., allowDotAsName=FALSE)

### Arguments

`x` |
a formula. |

`specials` |
which functions in the formula should be marked as
special in the `terms` object. |

`abb` |
Not implemented in **R**. |

`data` |
a data frame from which the meaning of the special symbol
`.` can be inferred. It is unused if there is no `.` in
the formula. |

`neg.out` |
Not implemented in **R**. |

`keep.order` |
a logical value indicating whether the terms should
keep their positions. If `FALSE` the terms are reordered so
that main effects come first, followed by the interactions,
all second-order, all third-order and so on. Effects of a given
order are kept in the order specified. |

`simplify` |
should the formula be expanded and simplified, the
pre-1.7.0 behaviour? |

`...` |
further arguments passed to or from other methods. |

`allowDotAsName` |
normally `.` in a formula refers to the
remaining variables contained in `data` . Exceptionally,
`.` can be treated as a name for non-standard uses of formulae. |

### Details

Not all of the options work in the same way that they do in S and not
all are implemented.

### Value

A `terms.object`

object is returned. The object itself is
the re-ordered (unless `keep.order = TRUE`

) formula. In all
cases variables within an interaction term in the formula are
re-ordered by the ordering of the `"variables"`

attribute, which
is the order in which the variables occur in the formula.

### See Also

`terms`

, `terms.object`

[Package

*stats* version 2.2.1

Index]