| 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)
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 Infs
really are statements with a proper mathematical limit, see the many
examples below.
ANSI/IEEE 754 Floating-Point Standard.
Currently (6/1999), Bill M.'s billm@melbpc.org.au tutorial
and examples at
http://www.linuxsupportline.com/~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 . 2147483647 -2147483648 NA 3 NA
all(is.na(ix) != is.finite(ix) | is.infinite(ix)) # TRUE (still)
ix[3] == (iI <- as.integer(Inf))#> warning: inaccurate integer conversion!
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"