R: Assign a Value to a Name

assign {base} | R Documentation

## Assign a Value to a Name

### Description

Assign a value to a name in an environment.

### Usage

    assign(x, value, pos = -1, envir = as.environment(pos),
           inherits = FALSE, immediate = TRUE)
    x <- value
    x <<- value
    value -> x
    value ->> x

    x = value

### Arguments

`x` | a variable name (given as a quoted string in the function call).
`value` | a value to be assigned to `x`.
`pos` | where to do the assignment. By default, assigns into the current environment. See the details for other possibilities.
`envir` | the `environment` to use. See the details section.
`inherits` | should the enclosing frames of the environment be inspected?
`immediate` | an ignored compatibility feature.

### Details

The `pos` argument can specify the environment in which to assign the object in any of several ways: as an integer (the position in the `search` list); as the character string name of an element in the search list; or as an `environment` (including using `sys.frame` to access the currently active function calls). The `envir` argument is an alternative way to specify an environment, but is primarily there for back compatibility.

`assign` does not dispatch assignment methods, so it cannot be used to set elements of vectors, names, attributes, etc.

### Value

This function is invoked for its side effect, which is assigning `value` to the variable `x`. If no `envir` is specified, then the assignment takes place in the currently active environment.
If `inherits` is `TRUE`, enclosing environments of the supplied environment are searched until the variable `x` is encountered. The value is then assigned in the environment in which the variable is encountered. If the symbol is not encountered then assignment takes place in the user's workspace (the global environment).
If `inherits` is `FALSE`, assignment takes place in the initial frame of `envir`.

### Assignment Operators

There are three different assignment operators. The operators `<-` and `=` assign into the environment in which they are evaluated. The `<-` can be used anywhere, but the `=` is only allowed at the top level (that is, in the complete expression typed by the user) or as one of the subexpressions in a braced list of expressions.

The operators `<<-` and `->>` cause a search to made through the environment for an existing definition of the variable being assigned. If such a variable is found then its value is redefined, otherwise assignment takes place globally. Note that their differs from that in the S language, but is useful in conjunction with the scoping rules of R.

In all the assignment operator expressions, `x` can be a name or an expression defining a part of an object to be replaced (e.g., `z[[1]]`). The name does not need to be quoted, though it can be.

### See Also

`get`, `exists`, `environment`.

### Examples

    for(i in 1:6) { #-- Create objects  'r1', 'r2', ... 'r6' --
     nam <- paste("r",i, sep=".")
     assign(nam, 1:i)
    }
    ls(pat="^r..$")

    ##-- Global assignment within a function:
    myf <- function(x) {
     innerf <- function(x) assign("Global.res", x^2, env = .GlobalEnv)
     innerf(x+1)
    }
    myf(3)
    Global.res # 16

    a<-1:4
    assign("a[1]",2)
    a[1]==2          #FALSE
    get("a[1]")==2   #TRUE

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