# logical: Logical Vectors

## Description

Create or test for objects of type `"logical"`, and the basic logical constants.

## Usage

 ```1 2 3 4 5 6 7``` ```TRUE FALSE T; F logical(length = 0) as.logical(x, ...) is.logical(x) ```

## Arguments

 `length` A non-negative integer specifying the desired length. Double values will be coerced to integer: supplying an argument of length other than one is an error. `x` object to be coerced or tested. `...` further arguments passed to or from other methods.

## Details

`TRUE` and `FALSE` are reserved words denoting logical constants in the R language, whereas `T` and `F` are global variables whose initial values set to these. All four are `logical(1)` vectors.

Logical vectors are coerced to integer vectors in contexts where a numerical value is required, with `TRUE` being mapped to `1L`, `FALSE` to `0L` and `NA` to `NA_integer_`.

## Value

`logical` creates a logical vector of the specified length. Each element of the vector is equal to `FALSE`.

`as.logical` attempts to coerce its argument to be of logical type. For `factor`s, this uses the `levels` (labels). Like `as.vector` it strips attributes including names. Character strings `c("T", "TRUE", "True", "true")` are regarded as true, `c("F", "FALSE", "False", "false")` as false, and all others as `NA`.

`is.logical` returns `TRUE` or `FALSE` depending on whether its argument is of logical type or not.

## References

Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.

`NA`, the other logical constant.