numeric                 package:base                 R Documentation

Numeric Vectors

Description:

     Creates or tests for objects of type '"numeric"'.

Usage:

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

Arguments:

  length: desired length.

       x: object to be coerced or tested.

     ...: further arguments passed to or from other methods.

Details:

     '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 'is.numeric()' returns 'FALSE' for a factor via its
     '"factor"' method.

Value:

     '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 '"double"'). 'as.numeric' for factors
     yields the codes underlying the factor levels, not the numeric
     representation of the labels, see also 'factor'.

     'is.numeric' returns 'TRUE' if its argument is of mode '"numeric"'
     (type '"double"' or type '"integer"') and not a factor, and
     'FALSE' otherwise.

Note:

     _R has no single precision data type.  All real numbers are stored
     in double precision format_.

References:

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

Examples:

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

