| double {base} | R Documentation |
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, ...)
length |
desired length. |
x |
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 0.
It is identical to numeric (and real).
as.double is a generic function. It is identical to
as.numeric (and as.real). Methods should return an
object of base type "double".
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 as.single
and single are identical to as.double and double
except they set the attribute Csingle that is used in the
.C and .Fortran interface, and they are
intended only to be used in that context.
as.double and is.double are primitive, so
positional matching is used and any names of supplied arguments are
ignored. This may not be true of methods for as.double.
double creates a double-precision vector of the specified
length. The elements of the vector are all equal to 0.
as.double attempts to coerce its argument to be of double
type: like as.vector it strips attributes including
names. (To ensure that an object is of double type without
stripping attributes, use storage.mode.)
Character strings containing either a decimal representation or a
hexadecimal representation (starting with 0x or 0X) can
be converted. as.double for factors yields the codes underlying
the factor levels, not the numeric representation of the labels, see
also factor.
is.double returns TRUE or FALSE depending on
whether its argument is of double type or not.
It is a historical anomaly that R has three names for its
floating-point vectors, double, numeric
and real.
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" (there was
a formal class "double" prior to R 2.7.0).
real is deprecated and should not be used in new code.
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
class, but as.numeric (which is identical to as.double)
coerces to the class.
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.
integer, numeric, storage.mode.
is.double(1) all(double(3) == 0)