Can you share examples between functions with rOxygen2?

Question

I know one can group multiple functions under the same documentation with the @describeIn or the @rdname tags using rOxygen. This is fine for groups of function with a similar purpose/syntax.

However, I'm writing a package where a set of functions should almost always be executed as part of a workflow. To make things cleaner I want to have a single example to illustrate this workflow and display it for all of the involved functions.

I need to keep the functions in their separate documentation page because each of them have very different purposes, parameters and require a pretty extensive doc on their own. I don't want to confuse the reader by grouping all of it together.

Is it possible to to this? Can I, for instance, have a file with the example code and include it in all function documentation ?

Just in case that help, I included some dummy code below.

#' function1
#' 
#' This does stuff
#' 
#' @param a,b a and b
#' @return c
#' @export
#' @examples 
#' # step 1 : do this
#' C <- function1(a,b)
#' 
#' # step 2 : do that
#' D <- function2(C, e, f)
#' 
#' # step 3 : profit.
function1 <- function(a,b){
  return(a+b)
}

#' function2
#' 
#' This also does stuff
#' 
#' @param C could be from function1
#' @param e,f e and f
#' @return d
#' @export
#' @examples 
#' # step 1 : do this
#' C <- function1(a,b)
#' 
#' # step 2 : do that
#' D <- function2(C, e, f)
#' 
#' # step 3 : profit.
function2 <- function(C, e, f){
  return(C+e+f)
}

Answer 1

I've found a way to do this by using the @eval tag of Roxygen and storing my examples in a function returning the example code.

So in a package, you would for example have a shared_examples.R file like so :

function_examples <- function()
{
  ex <- "
@examples
# step 1 : do this
C <- function1(a,b)

# step 2 : do that
D <- function2(C, e, f)

# step 3 : profit.
"
  return(strsplit(ex, split = "\n")[[1]]) # needed to have line jumps in the doc
}

and then, your actual function documentation will look like this :

#' function1
#' 
#' This does stuff
#' 
#' @param a,b a and b
#' @return c
#' @export
#' @eval function_examples()
function1 <- function(a,b){
  return(a+b)
}

#' function2
#' 
#' This also does stuff
#' 
#' @param C could be from function1
#' @param e,f e and f
#' @return d
#' @export
#' @eval function_examples()
function2 <- function(C, e, f){
  return(C+e+f)
}

And now, the example is shared between these 2 functions!

I find this makes it pretty easy to centralize examples (or any shared documentation between functions), without having to rip your hair out repeating everything when updating.