| NA {base} | R Documentation |
NA is a logical constant of length 1 which contains a missing
value indicator. NA can be freely coerced to any other vector
type except raw.
The generic function is.na indicates which elements are missing.
The generic function is.na<- sets elements to NA.
NA is.na(x) ## S3 method for class 'data.frame': is.na(x) is.na(x) <- value
x |
an R object to be tested. |
value |
a suitable index vector for use with x. |
The NA of character type is distinct from the
string "NA". Programmers who need to specify an explicit
string NA should use as.character(NA) rather than
"NA", or set elements to NA using is.na<-.
is.na(x) works elementwise when x is a
list. It is generic: you can write methods to handle
specific classes of objects, see InternalMethods.
Function is.na<- may provide a safer way to set missingness.
It behaves differently for factors, for example.
The default method for is.na returns a logical vector of the same
“form” as its argument x, containing TRUE for those
elements marked NA or NaN (!) and FALSE
otherwise. dim, dimnames and names attributes
are preserved.
The method is.na.data.frame returns a logical matrix with the
same dimensions as the data frame, and with dimnames taken from the
row and column names of the data frame.
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.
Chambers, J. M. (1998) Programming with Data. A Guide to the S Language. Springer.
NaN, is.nan, etc.,
and the utility function complete.cases.
na.action, na.omit, na.fail
on how methods can be tuned to deal with missing values.
is.na(c(1, NA)) #> FALSE TRUE is.na(paste(c(1, NA))) #> FALSE FALSE (xx <- c(0:4)) is.na(xx) <- c(2, 4) xx #> 0 NA 2 NA 4