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% File src/library/base/man/which.Rd
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% File src/library/base/man/which.Rd
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% Part of the R package, http://www.R-project.org
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% Part of the R package, http://www.R-project.org
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% Copyright 1995-2010 R Core Team
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% Copyright 1995-2013 R Core Team
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% Distributed under GPL 2 or later
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% Distributed under GPL 2 or later
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\name{which}
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\name{which}
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\alias{which}
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\alias{which}
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\alias{arrayInd}
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\alias{arrayInd}
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   when \code{x} is an array?}
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   when \code{x} is an array?}
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 \item{ind}{integer-valued index vector, as resulting from
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 \item{ind}{integer-valued index vector, as resulting from
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   \code{which(x)}.}
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   \code{which(x)}.}
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 \item{.dim}{\code{\link{dim}(.)} integer vector}
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 \item{.dim}{\code{\link{dim}(.)} integer vector}
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 \item{.dimnames}{optional list of character \code{\link{dimnames}(.)},
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 \item{.dimnames}{optional list of character \code{\link{dimnames}(.)}.
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   If \code{useNames} is true, to be used for constructing dimnames for
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   \code{arrayInd()} (and hence, \code{which(*, arr.ind=TRUE)}).
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   If \code{\link{names}(.dimnames)} is not empty, these are used as
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   of which only \code{.dimnames[[1]]} is used.}
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   column names.  \code{.dimnames[[1]]} is used as row names.}
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 \item{useNames}{logical indicating if the value of \code{arrayInd()}
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 \item{useNames}{logical indicating if the value of \code{arrayInd()}
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   should have (non-null) dimnames at all.}
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   should have (non-null) dimnames at all.}
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}
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}
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\value{
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\value{
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  If \code{arr.ind == FALSE} (the default), an integer vector with
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  If \code{arr.ind == FALSE} (the default), an integer vector with
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which(ll)
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which(ll)
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which((1:12)\%\%2 == 0) # which are even?
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which((1:12)\%\%2 == 0) # which are even?
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which(1:10 > 3, arr.ind = TRUE)
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which(1:10 > 3, arr.ind = TRUE)
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( m <- matrix(1:12, 3, 4) )
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( m <- matrix(1:12, 3, 4) )
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which(m \%\% 3 == 0)
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div.3 <- m \%\% 3 == 0
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which(div.3)
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which(m \%\% 3 == 0, arr.ind = TRUE)
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which(div.3, arr.ind = TRUE)
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rownames(m) <- paste("Case", 1:3, sep = "_")
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rownames(m) <- paste("Case", 1:3, sep = "_")
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which(m \%\% 5 == 0, arr.ind = TRUE)
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which(m \%\% 5 == 0, arr.ind = TRUE)
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dim(m) <- c(2, 2, 3); m
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dim(m) <- c(2, 2, 3); m
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which(m \%\% 3 == 0, arr.ind = FALSE)
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which(div.3, arr.ind = FALSE)
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which(m \%\% 3 == 0, arr.ind = TRUE)
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which(div.3, arr.ind = TRUE)
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vm <- c(m)
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vm <- c(m)
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dim(vm) <- length(vm) #-- funny thing with  length(dim(...)) == 1
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dim(vm) <- length(vm) #-- funny thing with  length(dim(...)) == 1
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which(div.3, arr.ind = TRUE)
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\dontshow{
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dimnames(m) <- list(X = c("U", "V"), Z = c("y","z"), three = LETTERS[1:3])
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wm <- which(m \%\% 3 == 0, arr.ind = TRUE)
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vn <- vm; dimnames(vn) <- list(LETTERS[1:12])
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which(vm \%\% 3 == 0, arr.ind = TRUE)
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wv <- which(vn \%\% 3 == 0, arr.ind = TRUE)
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stopifnot(identical(wv, array(3L*(1:4), dim = c(4, 1),
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                              dimnames = list(c("C", "F", "I", "L"), "dim1"))),
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          identical(wm, array(c(1:2, 1:2, 2:1, 1:2, 1:3, 3L),
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                              dim = 4:3,
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                              dimnames = list(rep(c("U","V"),2),
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                                              c("X", "Z", "three"))))
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)
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}%dont
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}
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}
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\keyword{logic}
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\keyword{logic}
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\keyword{attribute}
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\keyword{attribute}