imap.Rd

% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/imap.R
\name{imap}
\alias{imap}
\alias{imap_lgl}
\alias{imap_chr}
\alias{imap_int}
\alias{imap_dbl}
\alias{imap_raw}
\alias{imap_dfr}
\alias{imap_dfc}
\alias{iwalk}
\title{Apply a function to each element of a vector, and its index}
\usage{
imap(.x, .f, ...)

imap_lgl(.x, .f, ...)

imap_chr(.x, .f, ...)

imap_int(.x, .f, ...)

imap_dbl(.x, .f, ...)

imap_raw(.x, .f, ...)

imap_dfr(.x, .f, ..., .id = NULL)

imap_dfc(.x, .f, ...)

iwalk(.x, .f, ...)
}
\arguments{
\item{.x}{A list or atomic vector.}

\item{.f}{A function, formula, or vector (not necessarily atomic).

If a \strong{function}, it is used as is.

If a \strong{formula}, e.g. \code{~ .x + 2}, it is converted to a function. There
are three ways to refer to the arguments:
\itemize{
\item For a single argument function, use \code{.}
\item For a two argument function, use \code{.x} and \code{.y}
\item For more arguments, use \code{..1}, \code{..2}, \code{..3} etc
}

This syntax allows you to create very compact anonymous functions.

If \strong{character vector}, \strong{numeric vector}, or \strong{list}, it
is converted to an extractor function. Character vectors index by name
and numeric vectors index by position; use a list to index by position
and name at different levels. Within a list, wrap strings in \code{\link[=get-attr]{get-attr()}}
to extract named attributes. If a component is not present, the value of
\code{.default} will be returned.}

\item{...}{Additional arguments passed on to \code{.f}.}

\item{.id}{Either a string or \code{NULL}. If a string, the output will contain
a variable with that name, storing either the name (if \code{.x} is named) or
the index (if \code{.x} is unnamed) of the input. If \code{NULL}, the default, no
variable will be created.

Only applies to \code{_dfr} variant.}
}
\value{
A vector the same length as \code{.x}.
}
\description{
\code{imap_xxx(x, ...)}, an indexed map, is short hand for
\code{map2(x, names(x), ...)} if \code{x} has names, or \code{map2(x, seq_along(x), ...)}
if it does not. This is useful if you need to compute on both the value
and the position of an element.
}
\examples{
# Note that when using the formula shortcut, the first argument
# is the value, and the second is the position
imap_chr(sample(10), ~ paste0(.y, ": ", .x))
iwalk(mtcars, ~ cat(.y, ": ", median(.x), "\\n", sep = ""))
}
\seealso{
Other map variants: \code{\link{invoke}},
  \code{\link{lmap}}, \code{\link{map2}},
  \code{\link{map}}, \code{\link{modify}}
}