R help - Jul 2015 - Function returning multiple objects but printing only one

Hello,

Sorry if this has already been addressed before but I could not find any
helpful references.

I would like to create a function that outputs a single element of a list
but stores all elements, similar to  'lm' and many other functions.
There
are several answers on how to return multiple objects with lists, for
example:

http://r.789695.n4.nabble.com/How-to-return-multiple-values-in-a-function-td858528.html

http://stackoverflow.com/questions/8936099/returning-multiple-objects-in-an-r-function

But the examples show how to print multiple outputs, such as

functionReturningTwoValues <- function() {return(list(first=1, second=2))}
functionReturningTwoValues()

And I only want the function to print a single element from the list but
still store the other elements such that they can be retrieved with
functionReturningTwoValues$first, for example. My function produces
bootstrap coefficients so clearly I don't want to print the bootstrap
output but I do want users to be able to access it.

Many thanks,
Daniel

	[[alternative HTML version deleted]]

On 13/07/2015 5:06 PM, Daniel Caro wrote:
> Hello,
> 
> Sorry if this has already been addressed before but I could not find any
> helpful references.
> 
> I would like to create a function that outputs a single element of a list
> but stores all elements, similar to  'lm' and many other functions.
There
> are several answers on how to return multiple objects with lists, for
> example:
> 
>
http://r.789695.n4.nabble.com/How-to-return-multiple-values-in-a-function-td858528.html
> 
>
http://stackoverflow.com/questions/8936099/returning-multiple-objects-in-an-r-function
> 
> But the examples show how to print multiple outputs, such as
> 
> functionReturningTwoValues <- function() {return(list(first=1,
second=2))}
> functionReturningTwoValues()
> 
> And I only want the function to print a single element from the list but
> still store the other elements such that they can be retrieved with
> functionReturningTwoValues$first, for example. My function produces
> bootstrap coefficients so clearly I don't want to print the bootstrap
> output but I do want users to be able to access it.
You need to give your object a class, and define a print method for that
class.  It's pretty simple:


functionReturningTwoValues <- function() {return(structure(list(first=1,
second=2), class="MyClass"))}

print.MyClass <- function(x, ...) {
  print(x$first, ...)
}

This is using "S3 classes".  There are other systems (S4, etc.) that
let
you do this, but none are simpler.

Duncan Murdoch

Daniel,

I'm not sure if this is what you're after, but you could include a
print()
call in your function.  For example:

myfun <- function(x) {
  m1 <- min(x)
  m2 <- mean(x)
  m3 <- max(x)
  out <- list(m1, m2, m3)
  print(out[[2]])
  return(out)
}

result <- myfun(1:10)

?Jean
?

On Mon, Jul 13, 2015 at 4:06 PM, Daniel Caro <dcarov at gmail.com> wrote:
> Hello,
>
> Sorry if this has already been addressed before but I could not find any
> helpful references.
>
> I would like to create a function that outputs a single element of a list
> but stores all elements, similar to  'lm' and many other functions.
There
> are several answers on how to return multiple objects with lists, for
> example:
>
>
>
http://r.789695.n4.nabble.com/How-to-return-multiple-values-in-a-function-td858528.html
>
>
>
http://stackoverflow.com/questions/8936099/returning-multiple-objects-in-an-r-function
>
> But the examples show how to print multiple outputs, such as
>
> functionReturningTwoValues <- function() {return(list(first=1,
second=2))}
> functionReturningTwoValues()
>
> And I only want the function to print a single element from the list but
> still store the other elements such that they can be retrieved with
> functionReturningTwoValues$first, for example. My function produces
> bootstrap coefficients so clearly I don't want to print the bootstrap
> output but I do want users to be able to access it.
>
> Many thanks,
> Daniel
>
>         [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
	[[alternative HTML version deleted]]