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\name{is_nonna}
\alias{is_nonna}
\alias{is_nonna,ANY-method}
\alias{nnacount}
\alias{nnacount,ANY-method}
\alias{nnawhich}
\alias{nnawhich,ANY-method}
\alias{nnavals}
\alias{nnavals,ANY-method}
\alias{nnavals<-}
\alias{nnavals<-,ANY-method}
\title{is_nonna() and the nna*() functions}
\description{
A set of functions for direct manipulation of the non-NA elements
of an array-like object.
}
\usage{
is_nonna(x)
nnacount(x)
nnawhich(x, arr.ind=FALSE)
nnavals(x)
nnavals(x) <- value
}
\arguments{
\item{x}{
Typically (but not necessarily) an array-like object that is
\emph{non-NA sparse}, like an \link{NaArray} object.
However, \code{x} can also be an ordinary matrix or array, or any
matrix-like or array-like object.
}
\item{arr.ind}{
If \code{arr.ind=FALSE} (the default), the indices of the non-NA
array elements are returned in a numeric vector (a.k.a. \emph{L-index}).
Otherwise, they're returned in an ordinary matrix (a.k.a. \emph{M-index}).
See \code{?\link[S4Arrays]{Lindex}} in the \pkg{S4Arrays} package for
more information about \emph{L-index} and \emph{M-index}, and how to
convert from one to the other.
Note that using \code{arr.ind=TRUE} won't work if \code{nnacount(x)}
is >= \code{.Machine$integer.max} (= 2^31), because, in that case,
the returned \emph{M-index} would need to be a matrix with more rows
than what is supported by base R.
}
\item{value}{
A vector, typically of length \code{nnacount(x)} (or 1) and type
\code{type(x)}.
}
}
\details{
\code{nnacount(x)} and \code{nnawhich(x)} are equivalent to, but
typically more efficient than, \code{sum(is_nonna(x))} and
\code{which(is_nonna(x))}, respectively.
\code{nnavals(x)} is equivalent to, but typically more efficient than,
\code{x[nnawhich(x)]} (or \code{x[is_nonna(x)]}).
\code{nnavals(x) <- value} replaces the values of the non-NA array
elements in \code{x} with the supplied values. It's equivalent to,
but typically more efficient than, \code{x[nnawhich(x)] <- value}.
Note that \code{nnavals(x) <- nnavals(x)} is guaranteed to be a no-op.
}
\value{
\code{is_nonna()}: An array-like object of \code{type()} \code{"logical"}
and same dimensions as the input object.
\code{nnacount()}: The number of non-NA array elements in \code{x}.
\code{nnawhich()}: The indices of the non-NA array elements in \code{x},
either as an \emph{L-index} (if \code{arr.ind} is \code{FALSE}) or as
an \emph{M-index} (if \code{arr.ind} is \code{TRUE}).
Note that the indices are returned sorted in strictly ascending order.
\code{nnavals()}: A vector of the same \code{type()} as \code{x} and
containing the values of the non-NA array elements in \code{x}.
Note that the returned vector is guaranteed to be \emph{parallel}
to \code{nnawhich(x)}.
}
\seealso{
\itemize{
\item \link{is_nonzero} for \code{is_nonzero()} and \code{nz*()} functions
\code{nzcount()}, \code{nzwhich()}, etc...
\item \link{NaArray} objects.
\item Ordinary \link[base]{array} objects in base R.
\item \code{base::\link[base]{which}} in base R.
}
}
\examples{
a <- array(NA_integer_, dim=c(5, 12, 2))
a[sample(length(a), 20)] <- (-9):10
is_nonna(a)
## Get the number of non-NA array elements in 'a':
nnacount(a)
## nnawhich() returns the indices of the non-NA array elements in 'a'.
## Either as a "L-index" i.e. an integer (or numeric) vector of
## length 'nnacount(a)' containing "linear indices":
nnaidx <- nnawhich(a)
length(nnaidx)
head(nnaidx)
## Or as an "M-index" i.e. an integer matrix with 'nnacount(a)' rows
## and one column per dimension where the rows represent "array indices"
## (a.k.a. "array coordinates"):
Mnnaidx <- nnawhich(a, arr.ind=TRUE)
dim(Mnnaidx)
## Each row in the matrix is an n-tuple representing the "array
## coordinates" of a non-NA element in 'a':
head(Mnnaidx)
tail(Mnnaidx)
## Extract the values of the non-NA array elements in 'a' and return
## them in a vector "parallel" to 'nnawhich(a)':
a_nnavals <- nnavals(a) # equivalent to 'a[nnawhich(a)]'
length(a_nnavals)
head(a_nnavals)
nnavals(a) <- 10 ^ nnavals(a)
a
## Sanity checks:
stopifnot(
identical(nnaidx, which(!is.na(a))),
identical(Mnnaidx, which(!is.na(a), arr.ind=TRUE, useNames=FALSE)),
identical(nnavals(a), a[nnaidx]),
identical(nnavals(a), a[Mnnaidx]),
identical(`nnavals<-`(a, nnavals(a)), a)
)
}
\keyword{array}
\keyword{methods}
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