double(length = 0)
as.double(x, ...)
is.double(x)
single(length = 0)
as.single(x, ...)
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
precision. See .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.double
and numeric
(and formerly had 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"
. 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.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
. as.double
is a generic function. It is identical to
as.numeric
. 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.
https://en.wikipedia.org/wiki/IEEE_754-1985, https://en.wikipedia.org/wiki/IEEE_754-2008, https://en.wikipedia.org/wiki/Double_precision, https://en.wikipedia.org/wiki/Denormal_number.
http://grouper.ieee.org/groups/754/ for links to information on the standards.
integer
, numeric
, storage.mode
.
is.double(1)
all(double(3) == 0)
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