What are the differences and use cases of the five Magrittr Pipes %>%, %<>%, %$%, %!>% and %T>%?

Question

Magrittr has those different pipes:

• %>% Pipe
• %<>% Assignment pipe
• %$% Exposition pipe
• %!>% Eager pipe
• %T>% Tee pipe

What are their differences and use cases?

Answer 1

%>% Pipe

Pipe an object forward into a function or call expression.

library(magrittr)
1:10 %>% head()   # Basic use
#[1] 1 2 3 4 5 6
1:10 %>% head     # Works also
#[1] 1 2 3 4 5 6
#1:3 %>% approxfun(1:3, 4:6)  #But in this case empty parentheses are needed
#Error in if (is.na(method)) stop("invalid interpolation method") :
1:3 %>% approxfun(1:3, 4:6)()
#[1] 4 5 6

1:10 %>% head(3)  # Use with lhs as first argument
#[1] 1 2 3

"Ceci n'est pas une pipe" %>% gsub("une", "un", .)  # Using the dot place-holder
#[1] "Ceci n'est pas un pipe"

1:3 %>% paste0(LETTERS[.], 0)    # When dot is nested, lhs is still placed first
#[1] "1A0" "2B0" "3C0"
1:3 %>% {paste0(LETTERS[.], 0)}  # This can be avoided with {}
#[1] "A0" "B0" "C0"

See also: What are the disadvantages when using a function without empty parentheses with %>% the pipe of magrittr?.

%<>% Assignment pipe

Pipe an object forward into a function or call expression and update the lhs object with the resulting value.

x <- -2:2
x %<>% abs %>% sort
x  # 0 1 1 2 2

%$% Exposition pipe

Expose the names in lhs to the rhs expression. This is useful when functions do not have a built-in data argument.

iris %$% cor(Sepal.Length, Sepal.Width)
#[1] -0.1175698

See also: Should I use %$% instead of %>%?.

%!>% Eager pipe

Evaluate from left to right. Whereas %>% is lazy and only evaluates the piped expressions when needed, %!>% is eager and evaluates the piped input at each step. Also it evaluates in the same environment.

0 %!>% (\(x) {cat(1); x}) %!>% (\(x) cat(2))  # Evaluates from left to right
#12
0 %>% (\(x) {cat(1); x}) %>% (\(x) cat(2))    # Evaluates only cat(2) as the first result is never used
#2

1 %!>% assign("a", .)  # Work
a
#[1] 1
0 %>% assign("a", .)   # Does not work as there is an additional environment
a
#[1] 1
0 %>% assign("a", ., envir=parent.env(environment())) # Give explicitly where to evaluate
a
#[1] 0

%T>% Tee pipe

Pipe a value forward into a function- or call expression and return the original value instead of the result. This is useful when an expression is used for its side-effect, say plotting or printing.

matrix(1:4, 2) %T>% plot %>% sum  # sum gets the same data like plot
#[1] 10

See also: magrittr tee pipe %T>% equivalent.