| pipeOp | R Documentation |
Pipe a value into a call expression or a function expression.
lhs |> rhs
lhs |
expression producing a value. |
rhs |
a call expression or an expression of the form
|
A pipe expression passes, or pipes, the result of the left-hand side
expression lhs to the right-hand side expression rhs.
If the rhs expression is a call, then the lhs is
inserted as the first argument in the call. So x |> f(y) is
interpreted as f(x, y).
To avoid ambiguities, functions in rhs calls may not be
syntactically special, such as + or if.
Pipe notation allows a nested sequence of calls to be written in a way that may make the sequence of processing steps easier to follow.
Currently, pipe operations are implemented as syntax transformations.
So an expression written as x |> f(y) is parsed as f(x,
y). It is worth emphasizing that while the code in a pipeline is
written sequentially, regular R semantics for evaluation apply and
so piped expressions will be evaluated only when first used in the
rhs expression.
Returns the result of evaluating the transformed expression.
The forward pipe operator is motivated by the pipe introduced in the magrittr package, but is more streamlined. It is similar to the pipe or pipeline operators introduced in other languages, including F#, Julia, and JavaScript.
# simple uses:
mtcars |> head() # same as head(mtcars)
mtcars |> head(2) # same as head(mtcars, 2)
mtcars |> subset(cyl == 4) |> nrow() # same as nrow(subset(mtcars, cyl == 4))
# passing the lhs into an argument other than the first:
mtcars |> subset(cyl == 4) |> (function(d) lm(mpg ~ disp, data = d))()
# the pipe operator is implemented as a syntax transformation:
quote(mtcars |> subset(cyl == 4) |> nrow())
# regular R evaluation semantics apply
stop() |> (function(...) {})() # stop() is not used on RHS so is not evaluated
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