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).
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.)
is.finite(x) is.infinite(x) Inf NaN is.nan(x)
x |
(numerical) object to be tested. |
is.finite
returns a vector of the same length as x
the jth element of which is TRUE
if x[j]
is
finite (i.e., it is not one of the values NA
, NaN
,
Inf
or -Inf
). All elements of character and
generic (list) vectors are false, so is.finite
is only useful for
logical, integer, numeric and complex vectors. Complex numbers are
finite if both the real and imaginary parts are.
is.infinite
returns a vector of the same length as x
the jth element of which is TRUE
if x[j]
is
infinite (i.e., equal to one of Inf
or -Inf
). This will
be false unless x
is numeric or complex. Complex numbers are
infinite if either the real and 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.
In most ports of R one of these is used for the numeric missing
value NA
. It is generic: you can write methods to handle
specific classes of objects, see InternalMethods.
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 Inf
s
really are statements with a proper mathematical limit.
The IEC 60559 standard, also know as the ANSI/IEEE 754 Floating-Point Standard.
D. Goldberg (1991) What Every Computer Scientist Should Know
about Floating-Point Arithmetic ACM Computing Surveys, 23(1).
Postscript version available at
http://www.validlab.com/goldberg/paper.ps
http://grouper.ieee.org/groups/754/ for accessible information.
The C99 function isfinite
is used for is.finite
if available.
NA
, ‘Not Available’ which is not a number
as well, however usually used for missing values and applies to many
modes, not just numeric.
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)