| 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.
The generic function 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 generic function is.na<- sets elements to NA.
NA is.na(x) is.na.data.frame(x) is.na(x) <- value
x |
an R object to be tested. |
value |
a suitable index vector for use with x. |
For character vectors the value "NA" represents missingness.
is.na(x) works elementwise when x is a list.
The method dispatching is C-internal, rather than via
UseMethod.
Function is.na<- may provide a safer way to set missingness.
It behaves differently for factors, for example.
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)) #> F TRUE is.na(paste(c(1,NA)))#> F FALSE