**Numeric Vectors**

Creates or tests for objects of type `“numeric”`

.

numeric(length = 0) as.numeric(x, ...) is.numeric(x)

`length` | desired length. |
---|---|

`x` | object to be coerced or tested. |

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

`as.numeric`

is a generic function, but methods must be written for `as.double`

, which it calls.

`is.numeric`

is generic: you can write methods to handle specific classes of objects, see InternalMethods.

Note that factors are false for `is.numeric`

since there is a `“factor”`

method.

`numeric`

creates a real vector of the specified length. The elements of the vector are all equal to `0`

.

`as.numeric`

attempts to coerce its argument to a numeric type (either integer or real). `as.numeric`

for factors yields the codes underlying the factor levels, not the numeric representation of the labels.

`is.numeric`

returns `TRUE`

if its argument is of mode `“numeric”`

(type `“double”`

or type `“integer”`

) and not a factor, and `FALSE`

otherwise.

* has no single precision data type. All real numbers are
stored in double precision format*.

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

as.numeric(c("-.1"," 2.7 ","B")) # (-0.1, 2.7, NA) + warning as.numeric(factor(5:10))