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.
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)