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\alias{bquote}
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\alias{bquote}
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\title{Partial substitution in expressions}
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\title{Partial substitution in expressions}
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\description{
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\description{
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  An analogue of the LISP backquote macro.  \code{bquote} quotes its
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  An analogue of the LISP backquote macro.  \code{bquote} quotes its
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  argument except that terms wrapped in \code{.()} are evaluated in the
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  argument except that terms wrapped in \code{.()} are evaluated in the
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  specified \code{where} environment.
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  specified \code{where} environment. If \code{splice = TRUE} then
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  terms wrapped in \code{..()} are evaluated and spliced into a call.
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}
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}
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\usage{
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\usage{
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bquote(expr, where = parent.frame())
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bquote(expr, where = parent.frame(), splice = FALSE)
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}
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}
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\arguments{
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\arguments{
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  \item{expr}{A \link{language object}.}
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  \item{expr}{A \link{language object}.}
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  \item{where}{An environment.}
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  \item{where}{An environment.}
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  \item{splice}{Logical; if \code{TRUE} splicing is enabled.}
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}
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}
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\value{
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\value{
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  A \link{language object}.
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  A \link{language object}.
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}
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}
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plot(1:10, a*(1:10), main = bquote(a == .(a)))
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plot(1:10, a*(1:10), main = bquote(a == .(a)))
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## to set a function default arg
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## to set a function default arg
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default <- 1
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default <- 1
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bquote( function(x, y = .(default)) x+y )
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bquote( function(x, y = .(default)) x+y )
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exprs <- expression(x <- 1, y <- 2, x + y)
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bquote(function() {..(exprs)}, splice = TRUE)
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}
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}
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\keyword{programming}
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\keyword{programming}
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\keyword{data}
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\keyword{data}