Stepping through a pipeline with intermediate results

Question

Is there a way to output the result of a pipeline at each step without doing it manually? (eg. without selecting and running only the selected chunks)

I ofte

Answer 1

It is easy with magrittr function chain. For example define a function my_chain with:

foo <- function(x) x + 1
bar <- function(x) x + 1
baz <- function(x) x + 1
my_chain <- . %>% foo %>% bar %>% baz

and get the final result of a chain as:

     > my_chain(0)
    [1] 3

You can get a function list with functions(my_chain) and define a "stepper" function like this:

stepper <- function(fun_chain, x, FUN = print) {
  f_list <- functions(fun_chain)
  for(i in seq_along(f_list)) {
    x <- f_list[[i]](x)
    FUN(x)
  }
  invisible(x)
}

And run the chain with interposed print function:

stepper(my_chain, 0, print)

# [1] 1
# [1] 2
# [1] 3

Or with waiting for user input:

stepper(my_chain, 0, function(x) {print(x); readline()})