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 user's workspace and before all previously loaded packages and previously attached databases. This can be altered to attach later in the search path with the pos option, but you cannot attach at pos=1.

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 user's workspace (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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