How can I achieve partial application of a function before using it within a magrittR pipeline?

Question

I want to have parameterizable parts of pipelines.

This is the code I want to write:

library(magrittr)
d <- data.frame(x=1:5)
add_n <- function(n) . %>% transform(x = x + n)
d %>% add_n(3)

Obviously it doesn't work, because %>% sets d as the argument of add_n.

Answer 1

You can do the following:

add_n <- function(d, n) d %>% transform(x = x + n)
d %>% add_n(3)
#   x
# 1 4
# 2 5
# 3 6
# 4 7
# 5 8

%>% substitutes the first argument of the following function with the LHS, so your function needs a second argument.