I have written a function that produces as output 2 matrices, say A & B, and I have used list() in order to separate them in my output. Now I would like to re-write my function so that the displayed output is ONLY matrix B unless I specify it when calling the function (however, my function has still to compute both matrices.) Basically, I would like to hide matrix A from the output unless I say otherwise.
Can I do this in R?
Yes.
Here's an example:
myfun <- function(a, b, Bonly=TRUE) {
# calculations
result <- list(a, b)
if (Bonly) return(result[2]) else return(result)
}
Basically you set a variable that has a default in the function with the notation x=DEFAULT in the set of arguments passed to the function. The variable does not need to be specified for the function to run. If the variable has the default value then return just B, otherwise return both.
> myfun(1,2)
[[1]]
[1] 2
> myfun(1,2, FALSE)
[[1]]
[1] 1
[[2]]
[1] 2
You can set an argument with a default value saying that matrix A should hidden, unless the user specifies it should be part of the result
myFunction <- function(<your arguments>, hideA = TRUE){
#your computations
...
output <- list(A = <matrix A>, B = <matrix B>)
#your result
if(hideA) output <- output$B #hide A
return(output)
}
#calling the function
myFunction(<your args>) #A will be hidden by default
myFunction(<your args>, hideA = FALSE) #the list of matrix will be returned
