.BG
.VE $Header: /usr3/s/current/s/.help/RCS/na,v 1.2 83/12/30 19:31:16 rab Exp $
.FN na
.FN NA
.TL
na NA: Pick Out Missing Values
.CS
na(x)
NA(x)
.PP
.AG x
vector structure.
.RT
logical structure like `x', with TRUE wherever a missing
value (NA) appeared in `x', and FALSE elsewhere.
.SH NOTE
Whenever an NA appears in either operand of any logical operation,
the corresponding value is NA. In particular,
the expression `x==NA' will always
produce a vector of all NA's; the `na' function must be used to
test for missing values.
.KW missing
.KW logic
.KW basic*
.KW attribute
.WR
