[R] How to return more than one variable from function

[Vincent Goulet]

Le Vendredi 20 Avril 2007 11:23, vous avez écrit :
> From: Vincent Goulet
>
> > Le Vendredi 20 Avril 2007 07:46, Julien Barnier a écrit :
> > > Hi,
> > >
> > > > I have written a function which computes variance, sd,
> > > > r^2, R^2adj etc. But i am not able to return all of
> > > > them in return statement.
> > >
> > > You can return a vector, or a list.
> > >
> > > For example :
> > >
> > > func <- function() {
> > >   ...
> > >   result <- list(variance=3, sd=sqrt(3))
> > >   return(result)  # you can omit this
> > > }
> >
> > Nitpicking and for the record: if you omit the
> > "return(result)" line, the
> > function will return nothing since it ends with an
> > assignment.
>
> Have you actually checked?  Counterexample:
>
> R> f <- function(x) y <- 2 * x
> R> f(3)
> R> (z <- f(3))
> [1] 6
> R> f2 <- function(x) { y <- 2 * x; y }
> R> f2(3)
> [1] 6

Got me here. I should have written "will not *print* anything". Still new 
useRs should avoid assigning in the last line of a function to the risk of 
thinking their function "does nothing".

> > Furthermore,
> > explicit use of return() is never needed at the end of a
> > function. The above
> > snippet is correct, but this is enough:
> >
> > func <- function() {
> >   ...
> >   result <-list(variance=3, sd=sqrt(3))
> >   result
> > }
> >
> > But then, why assign to a variable just to return its value?
> > Better still:
> >
> > func <- function() {
> >   ...
> >   list(variance=3, sd=sqrt(3))
> > }
>
> Or, as has been suggested, if all values to be returned are of the same
> type, just use a (named) vector:
>
> func <- function(...) {
>     ...
>     c(Variance=3, "R-squared"=0.999)
> }
>
> Andy
>
> > > a <- func()
> > > a$variance
> > > a$sd
> > >
> > > HTH,
> > >
> > > Julien
> >
> > --
> >   Vincent Goulet, Professeur agrégé
> >   École d'actuariat
> >   Université Laval, Québec
> >   Vincent.Goulet at act.ulaval.ca   http://vgoulet.act.ulaval.ca
> >
> > ______________________________________________
> > R-help at stat.math.ethz.ch mailing list
> > 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.
>
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-- 
  Vincent Goulet, Associate Professor
  École d'actuariat
  Université Laval, Québec 
  Vincent.Goulet at act.ulaval.ca   http://vgoulet.act.ulaval.ca