magrittr

You can use the . placeholder multiple times in a right-hand side expression.

Important Behavior: If the placeholder only appears inside nested expressions, magrittr applies the 'first-argument rule' (automatically passing the LHS to the first argument of the first function). To force the use of the placeholder for specific arguments in nested expressions, enclose the right-hand side in braces {}.

• x %>% f(y = nrow(.), z = ncol(.)) is equivalent to f(x, y = nrow(x), z = ncol(x)) (due to the first-argument rule).
• x %>% {f(y = nrow(.), z = ncol(.))} is equivalent to f(y = nrow(x), z = ncol(x)) (overruling the rule with braces).

The %>% operator pipes the left-hand side value into the first argument of the function on the right-hand side. This allows for structuring data operations from left-to-right, avoiding nested function calls and temporary variables.

• x %>% f is equivalent to f(x)
• x %>% f(y) is equivalent to f(x, y)
• x %>% f %>% g %>% h is equivalent to h(g(f(x)))

the_data <-
  read.csv('/path/to/data/file.csv') %>%
  subset(variable_a > x) %>%
  transform(variable_c = variable_a/variable_b) %>%
  head(100)

You can install magrittr as part of the full tidyverse suite, as a standalone package from CRAN, or via GitHub using pak or devtools.

# The easiest way to get magrittr is to install the whole tidyverse:
install.packages("tidyverse")

# Alternatively, install just magrittr:
install.packages("magrittr")

# Or the development version from GitHub:
# install.packages("devtools")
pak::pak("tidyverse/magrittr")

A pipeline starting with the . returns a function. This allows you to build new functions by composing existing ones using the pipe.

f <- . %>% cos %>% sin 
# is equivalent to 
f <- function(.) sin(cos(.))

The dot . acts as a placeholder for the left-hand side value. This is useful when you want to pass the piped value to an argument other than the first one.

• x %>% f(y, .) is equivalent to f(y, x)
• x %>% f(y, z = .) is equivalent to f(y, z = x)

# Example of using the placeholder for a non-first argument
x %>% f(y, z = .)

The %$% operator (exposition operator) allows you to expose the variables within a data object (like a data frame) to the right-hand side expression. This is useful for functions that do not have a formal data argument but operate on variables within a data structure.

iris %>%
  subset(Sepal.Length > mean(Sepal.Length)) %$% 
  cor(Sepal.Length, Sepal.Width)

data.frame(z = rnorm(100)) %$% 
  ts.plot(z)