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% File src/library/base/man/numeric.Rd
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% File src/library/base/man/numeric.Rd
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% Part of the R package, https://www.R-project.org
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% Part of the R package, https://www.R-project.org
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% Copyright 1995-2014 R Core Team
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% Copyright 1995-2016 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{numeric}
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\name{numeric}
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\title{Numeric Vectors}
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\title{Numeric Vectors}
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\alias{numeric}
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\alias{numeric}
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  (\link{type} \code{"double"} or type \code{"integer"}) and not a
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  (\link{type} \code{"double"} or type \code{"integer"}) and not a
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  factor, and \code{FALSE} otherwise.  That is,
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  factor, and \code{FALSE} otherwise.  That is,
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  \code{is.integer(x) || is.double(x)}, or
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  \code{is.integer(x) || is.double(x)}, or
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  \code{(mode(x) == "numeric") && !is.factor(x)}.
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  \code{(mode(x) == "numeric") && !is.factor(x)}.
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}
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}
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\section{Warning}{
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  If \code{x} is a \code{\link{factor}}, \code{as.numeric} will return
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  the underlying numeric (integer) representation, which is often
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  meaningless as it may not correspond to the \code{factor}
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  \code{\link{levels}}, see the \sQuote{Warning} section in
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  \code{\link{factor}} (and the 2nd example below).
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}
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\section{S4 methods}{
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\section{S4 methods}{
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  \code{as.numeric} and \code{is.numeric} are internally S4 generic and
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  \code{as.numeric} and \code{is.numeric} are internally S4 generic and
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  so methods can be set for them \emph{via} \code{setMethod}.
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  so methods can be set for them \emph{via} \code{setMethod}.
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  To ensure that \code{as.numeric} and \code{as.double}
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  To ensure that \code{as.numeric} and \code{as.double}
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  \emph{The New S Language}.
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  \emph{The New S Language}.
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  Wadsworth & Brooks/Cole.
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  Wadsworth & Brooks/Cole.
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}
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}
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\examples{
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\examples{
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as.numeric(c("-.1"," 2.7 ","B")) # (-0.1, 2.7, NA)  +  warning
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as.numeric(c("-.1"," 2.7 ","B")) # (-0.1, 2.7, NA)  +  warning
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as.numeric(factor(5:10)) # not what you'd expect
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f <- factor(1:5)
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## what you typically meant and want:
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as.numeric(factor(5:10))
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as.numeric(as.character(f))
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## the same, considerably (for long factors) more efficient:
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as.numeric(levels(f))[f]
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}
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}
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\keyword{classes}
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\keyword{classes}
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\keyword{attribute}
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\keyword{attribute}