52 lines
2.0 KiB
R
52 lines
2.0 KiB
R
% Generated by roxygen2: do not edit by hand
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% Please edit documentation in R/utils-tidy-eval.R
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\name{tidyeval}
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\alias{tidyeval}
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\alias{expr}
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\alias{enquo}
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\alias{enquos}
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\alias{sym}
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\alias{syms}
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\alias{.data}
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\alias{:=}
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\alias{as_name}
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\alias{as_label}
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\title{Tidy eval helpers}
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\description{
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\itemize{
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\item \code{\link[rlang]{sym}()} creates a symbol from a string and
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\code{\link[rlang:sym]{syms}()} creates a list of symbols from a
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character vector.
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\item \code{\link[rlang:nse-defuse]{enquo}()} and
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\code{\link[rlang:nse-defuse]{enquos}()} delay the execution of one or
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several function arguments. \code{enquo()} returns a single quoted
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expression, which is like a blueprint for the delayed computation.
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\code{enquos()} returns a list of such quoted expressions.
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\item \code{\link[rlang:nse-defuse]{expr}()} quotes a new expression \emph{locally}. It
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is mostly useful to build new expressions around arguments
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captured with \code{\link[=enquo]{enquo()}} or \code{\link[=enquos]{enquos()}}:
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\code{expr(mean(!!enquo(arg), na.rm = TRUE))}.
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\item \code{\link[rlang]{as_name}()} transforms a quoted variable name
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into a string. Supplying something else than a quoted variable
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name is an error.
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That's unlike \code{\link[rlang]{as_label}()} which also returns
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a single string but supports any kind of R object as input,
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including quoted function calls and vectors. Its purpose is to
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summarise that object into a single label. That label is often
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suitable as a default name.
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If you don't know what a quoted expression contains (for instance
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expressions captured with \code{enquo()} could be a variable
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name, a call to a function, or an unquoted constant), then use
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\code{as_label()}. If you know you have quoted a simple variable
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name, or would like to enforce this, use \code{as_name()}.
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}
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To learn more about tidy eval and how to use these tools, visit
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\url{https://tidyeval.tidyverse.org} and the
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\href{https://adv-r.hadley.nz/metaprogramming.html}{Metaprogramming
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section} of \href{https://adv-r.hadley.nz}{Advanced R}.
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}
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\keyword{internal}
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