Create, coerce to or test for a double-precision vector.
double(length = 0) as.double(x, ...) is.double(x)single(length = 0) as.single(x, ...)
- 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.
- object to be coerced or tested.
- further arguments passed to or from other methods.
double creates a double-precision vector of the specified
length. The elements of the vector are all equal to
It is identical to
as.double is a generic function. It is identical to
as.numeric. Methods should return an object of base type
is.double is a test of double type.
R has no single precision data type. All real numbers are
stored in double precision format. The functions
single are identical to
except they set the attribute
Csingle that is used in the
.Fortran interface, and they are
intended only to be used in that context.
doublecreates a double-precision vector of the specified length. The elements of the vector are all equal to
as.doubleattempts to coerce its argument to be of double type: like
as.vectorit strips attributes including names. (To ensure that an object is of double type without stripping attributes, use
storage.mode.) Character strings containing optional whitespace followed by either a decimal representation or a hexadecimal representation (starting with
0X) can be converted, as can special values such as
"infinity", irrespective of case.
as.doublefor factors yields the codes underlying the factor levels, not the numeric representation of the labels, see also
FALSEdepending on whether its argument is of double type or not.
All R platforms are required to work with values conforming to the
IEC 60559 (also known as IEEE 754) standard. This basically works
with a precision of 53 bits, and represents to that precision a range
of absolute values from about $2e-308$ to
$2e+308$. It also has special values
NaN (many of them), plus and minus infinity and plus and
minus zero (although R acts as if these are the same). There are
also denormal(ized) (or subnormal) numbers with absolute
values above or below the range given above but represented to less
.Machine for precise information on these limits.
Note that ultimately how double precision numbers are handled is down
to the CPU/FPU and compiler. In IEEE 754-2008/IEC60559:2011 this is called binary64 format.
Note on names
It is a historical anomaly that R has two names for its
(and formerly had
double is the name of the type.
numeric is the name of the mode and also of the implicit
class. As an S4 formal class, use
"numeric". The potential confusion is that R has used mode
"numeric" to mean double or integer, which conflicts
with the S4 usage. Thus
is.numeric tests the mode, not the
as.numeric (which is identical to
coerces to the class.
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.
http://grouper.ieee.org/groups/754/ for links to information on the standards.
is.double(1) all(double(3) == 0)