Is there a way to pipe in base R, without having to define your own function (i.e. something 'out of the box'), and without having to load any external packages?
That is, some (base R) alternative to the magrittr pipe %>%. Possibly in a forthcoming version of R (?)
Is this functionality available in R 4.0.3. If not, which R version is it found in, and if so, how is this achieved?
In R |> is used as a pipe operator. (Since 4.1.0)
The left-hand side expression lhs is inserted as the first free argument in the call of to the right-hand side expression rhs.
mtcars |> head() # same as head(mtcars)
# mpg cyl disp hp drat wt qsec vs am gear carb
#Mazda RX4 21.0 6 160 110 3.90 2.620 16.46 0 1 4 4
#Mazda RX4 Wag 21.0 6 160 110 3.90 2.875 17.02 0 1 4 4
#Datsun 710 22.8 4 108 93 3.85 2.320 18.61 1 1 4 1
#Hornet 4 Drive 21.4 6 258 110 3.08 3.215 19.44 1 0 3 1
#Hornet Sportabout 18.7 8 360 175 3.15 3.440 17.02 0 0 3 2
#Valiant 18.1 6 225 105 2.76 3.460 20.22 1 0 3 1
mtcars |> head(2) # same as head(mtcars, 2)
# mpg cyl disp hp drat wt qsec vs am gear carb
#Mazda RX4 21 6 160 110 3.9 2.620 16.46 0 1 4 4
#Mazda RX4 Wag 21 6 160 110 3.9 2.875 17.02 0 1 4 4
It is also possible to use a named argument with the placeholder _ in the rhs call to specify where the lhs is to be inserted. The placeholder can only appear once on the rhs. (Since 4.2.0)
mtcars |> lm(mpg ~ disp, data = _)
#mtcars |> lm(mpg ~ disp, _) #Error: pipe placeholder can only be used as a named argument
#Call:
#lm(formula = mpg ~ disp, data = mtcars)
#
#Coefficients:
#(Intercept) disp
# 29.59985 -0.04122
Alternatively explicitly name the argument(s) before the "one":
mtcars |> lm(formula = mpg ~ disp)
In case the placeholder is used more than once or used as a named or also unnamed argument on any position or for disabled functions: Use an (anonymous) function.
mtcars |> (\(.) .[.$cyl == 6,])()
#mtcars ->.; .[.$cyl == 6,] # Alternative using bizarro pipe
#local(mtcars ->.; .[.$cyl == 6,]) # Without overwriting and keeping .
# mpg cyl disp hp drat wt qsec vs am gear carb
#Mazda RX4 21.0 6 160.0 110 3.90 2.620 16.46 0 1 4 4
#Mazda RX4 Wag 21.0 6 160.0 110 3.90 2.875 17.02 0 1 4 4
#Hornet 4 Drive 21.4 6 258.0 110 3.08 3.215 19.44 1 0 3 1
#Valiant 18.1 6 225.0 105 2.76 3.460 20.22 1 0 3 1
#Merc 280 19.2 6 167.6 123 3.92 3.440 18.30 1 0 4 4
#Merc 280C 17.8 6 167.6 123 3.92 3.440 18.90 1 0 4 4
#Ferrari Dino 19.7 6 145.0 175 3.62 2.770 15.50 0 1 5 6
mtcars |> (\(.) lm(mpg ~ disp, .))()
#Call:
#lm(formula = mpg ~ disp, data = .)
#
#Coefficients:
#(Intercept) disp
# 29.59985 -0.04122
1:3 |> setNames(object = _, nm = _)
#Error in setNames(object = "_", nm = "_") :
# pipe placeholder may only appear once
1:3 |> (\(.) setNames(., .))()
#1 2 3
#1 2 3
1:3 |> list() |> setNames(".") |> with(setNames(., .))
#1 2 3
#1 2 3
#The same but over a function
._ <- \(data, expr, ...) {
eval(substitute(expr), list(. = data), enclos = parent.frame())
}
1:3 |> ._(setNames(., .))
#1 2 3
#1 2 3
Some function are disabled.
1:3 |> `+`(4)
#Error: function '+' not supported in RHS call of a pipe
But some still can be called by placing them in round brackets, call them via the function ::, call it in a function or define a link to the function.
1:3 |> (`+`)(4)
#[1] 5 6 7
1:3 |> base::`+`(4)
#[1] 5 6 7
1:3 |> (\(.) . + 4)()
#[1] 5 6 7
fun <- `+`
1:3 |> fun(4)
#[1] 5 6 7
An expression written as x |> f(y) is parsed as f(x, y). While the code in a pipeline is written sequentially, regular R semantics for evaluation apply. So piped expressions will be evaluated only when first used in the rhs expression.
-1 |> sqrt() |> (\(x) 0)()
#[1] 0
. <- -1
. <- sqrt(.)
#Warning message:
#In sqrt(.) : NaNs produced
(\(x) 0)(.)
#[1] 0
x <- data.frame(a=0)
f1 <- \(x) {message("IN 1"); x$b <- 1; message("OUT 1"); x}
f2 <- \(x) {message("IN 2"); x$c <- 2; message("OUT 2"); x}
x|> f1() |> f2()
#IN 2
#IN 1
#OUT 1
#OUT 2
# a b c
#1 0 1 2
f2(f1(x))
#IN 2
#IN 1
#OUT 1
#OUT 2
# a b c
#1 0 1 2
. <- x
. <- f1(.)
#IN 1
#OUT 1
f2(.)
#IN 2
#OUT 2
# a b c
#1 0 1 2