| is.finite {base} | R Documentation |
is.finite and is.infinite return a vector of the same
length as x, indicating which elements are finite (not infinite
and not missing) or infinite.
Inf and -Inf are positive and negative infinity
whereas NaN means ‘Not a Number’. (These apply to numeric
values and real and imaginary parts of complex values but not to
values of integer vectors.) Inf and NaN (as well as
NA) are
reserved words in the R language.
is.finite(x)
is.infinite(x)
is.nan(x)
Inf
NaN
x |
R object to be tested: the default methods handle atomic vectors. |
is.finite returns a vector of the same length as x the
j-th element of which is TRUE if x[j] is finite (i.e., it
is not one of the values NA, NaN, Inf or
-Inf) and FALSE otherwise. Complex
numbers are finite if both the real and imaginary parts are.
is.infinite returns a vector of the same length as x the
j-th element of which is TRUE if x[j] is infinite (i.e.,
equal to one of Inf or -Inf) and FALSE
otherwise. This will be false unless x is numeric or complex.
Complex numbers are infinite if either the real or the imaginary part is.
is.nan tests if a numeric value is NaN. Do not test
equality to NaN, or even use identical, since
systems typically have many different NaN values. One of these is
used for the numeric missing value NA, and is.nan is
false for that value. A complex number is regarded as NaN if
either the real or imaginary part is NaN but not NA.
All elements of logical, integer and raw vectors are considered not to
be NaN.
All three functions accept NULL as input and return a length
zero result. The default methods accept character and raw vectors, and
return FALSE for all entries. Prior to R version 2.14.0 they
accepted all input, returning FALSE for most non-numeric
values; cases which are not atomic vectors are now signalled as
errors.
All three functions are generic: you can write methods to handle specific classes of objects, see InternalMethods.
A logical vector of the same length as x: dim,
dimnames and names attributes are preserved.
In R, basically all mathematical functions (including basic
Arithmetic), are supposed to work properly with
+/- Inf and NaN as input or output.
The basic rule should be that calls and relations with Infs
really are statements with a proper mathematical limit.
Computations involving NaN will return NaN or perhaps
NA: which of those two is not guaranteed and may depend
on the R platform (since compilers may re-order computations).
The IEC 60559 standard, also known as the ANSI/IEEE 754 Floating-Point Standard.
https://en.wikipedia.org/wiki/NaN.
D. Goldberg (1991).
What Every Computer Scientist Should Know about Floating-Point
Arithmetic.
ACM Computing Surveys, 23(1), 5–48.
doi:10.1145/103162.103163.
Also available at
https://docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.html.
The C99 function isfinite is used for is.finite.
NA, ‘Not Available’ which is not a number
as well, however usually used for missing values and applies to many
modes, not just numeric and complex.
pi / 0 ## = Inf a non-zero number divided by zero creates infinity
0 / 0 ## = NaN
1/0 + 1/0 # Inf
1/0 - 1/0 # NaN
stopifnot(
1/0 == Inf,
1/Inf == 0
)
sin(Inf)
cos(Inf)
tan(Inf)