is.finite {base} | R Documentation |
is.finite
and is.infinite
return a vector of the same
length as x
, indicating which elements are finite or not.
Inf
and -Inf
are positive and negative `infinity' whereas
NaN
means ``Not a Number''.
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
).
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
).
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, see the many
examples below.
ANSI/IEEE 754 Floating-Point Standard.
Currently (6/2002), Bill Metzenthen's billm@suburbia.net tutorial
and examples at
http://www.suburbia.net/~billm/
NA
, `Not Available' which is not a number
as well, however usually used for missing values.
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 ) exp(-Inf) == 0 ## (actually, the last one seems to give NA on not-very-new ## versions of Linux, which is a Linux bug and seems to be ## corrected in newer 'libc6' based Linuxen). stopifnot( is.na(0/0), !is.na(Inf), is.nan(0/0), !is.nan(NA) && !is.infinite(NA) && !is.finite(NA), is.nan(NaN) && !is.infinite(NaN) && !is.finite(NaN), !is.nan(c(1,NA)), c(FALSE,TRUE,FALSE) == is.nan(c (1,NaN,NA)), c(FALSE,TRUE,FALSE) == is.nan(list(1,NaN,NA))#-> FALSE in older versions ) lgamma(Inf) == Inf Inf + Inf == Inf Inf - Inf == NaN # NA --- should test with 'is.nan() (1/0) * (1/0)# Inf (1/0) / (1/0)# NaN pm <- c(-1,1) # 'pm' = plus/minus log(0) == - 1/0 exp(-Inf) == 0 sin(Inf) cos(Inf) tan(Inf) all(atan(Inf*pm) == pm*pi/2) # TRUE x <- c(100,-1e-13,Inf,-Inf, NaN, pi, NA) x # 1.000000 -3.000000 Inf -Inf NA 3.141593 NA names(x) <- formatC(x, dig=3) is.finite(x) ##- 100 -1e-13 Inf -Inf NaN 3.14 NA ##- T T . . . T . is.na(x) ##- 100 -1e-13 Inf -Inf NaN 3.14 NA ##- . . . . T . T which(is.na(x) & !is.nan(x))# only 'NA': 7 is.na(x) | is.finite(x) ##- 100 -1e-13 Inf -Inf NaN 3.14 NA ##- T T . . T T T is.infinite(x) ##- 100 -1e-13 Inf -Inf NaN 3.14 NA ##- . . T T . . . ##-- either finite or infinite or NA: all(is.na(x) != is.finite(x) | is.infinite(x)) # TRUE all(is.nan(x) != is.finite(x) | is.infinite(x)) # FALSE: have 'real' NA ##--- Integer (ix <- structure(as.integer(x),names= names(x))) ##- 100 -1e-13 Inf -Inf NaN 3.14 NA ##- 100 0 NA NA NA 3 NA all(is.na(ix) != is.finite(ix) | is.infinite(ix)) # TRUE (still) ix[3] == (iI <- as.integer(Inf))#> warning: NAs introduced by coercion ix[4] == (imI<- as.integer(-Inf)) iI == .Machine$integer.max # TRUE imI == -.Machine$integer.max # TRUE ##--- Overflow in simple integer arithmetic: as.integer(2)*iI # -2 as.integer(3)*iI # 2147483645 as.integer(3)*iI == iI-2 # TRUE storage.mode(ii <- -3:5) storage.mode(zm <- outer(ii,ii, FUN="*"))# integer storage.mode(zd <- outer(ii,ii, FUN="/"))# double range(zd, na.rm=TRUE)# -Inf Inf zd[,ii==0] (storage.mode(print(1:1 / 0:0)))# Inf "double" (storage.mode(print(1:1 / 1:1)))# 1 "double" (storage.mode(print(1:1 + 1:1)))# 2 "integer" (storage.mode(print(2:2 * 2:2)))# 4 "integer"