attach {base} | R Documentation

## Attach Set of R Objects to Search Path

### Description

The database is attached to the R search path. This means that the database is searched by R when evaluating a variable, so objects in the database can be accessed by simply giving their names.

### Usage

    attach(what, pos = 2, name = deparse(substitute(what)))

### Arguments

`what` | ``database''. This may currently be a `data.frame` or `list` or a R data file created with `save`.
`pos` | integer specifying position in `search()` where to attach.
`name` | alternative way to specify the database to be attached.

### Details

When evaluating a variable or function name R searches for that name in the databases listed by `search`. The first name of the appropriate type is used.

By attaching a data frame to the search path it is possible to refer to the variables in the data frame by their names alone, rather than as components of the data frame (eg in the example below, `height` rather than `women$height`).

By default the database is attached in position 2 in the search path, immediately after the R global environment and before all previously loaded packages and previously attached databases. This can be altered with the `pos` option.

Note that by default assignment is not performed in an attached database. Attempting to modify a variable or function in an attached database will actually create a modified version in the R global environment. For this reason `attach` can lead to confusion.

### Value

The `environment` is returned invisibly with a `"name"` attribute.

### See Also

`library`, `detach`, `search`, `objects`, `environment`.

### Examples

    data(women)
    summary(women$height) ## refers to variable `height' in the dataframe
    attach(women)
    summary(height)      ## The same variable now available by name
    height<-height*2.54  ## Don't do this. It creates a new variable
    detach("women")
    summary(height)      ## The new variable created by modifying `height'
    rm(height)

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