[R] sprintf() and return() oddity

[Raw, Jeremy, P.E.]

It's not a bug.  It's the intended behavior.

Sprintf by itself returns a formatted character string and doesn't print anything.  Without the return statement, the function returns the string, which the interactive processor then prints (since that's what it does when you simply present it with an object).

To get the same behavior inside the function and still return the value 'a', just do this:

x <- function() { a <- 888
+ print(sprintf("xxx %s", a) )
+ return(a) }

That just makes explicit what the combination of function + interaction is doing implicitly.

Good luck!

-- 
Jeremy Raw, PE, AICP 
Senior Modeling Systems Analyst 
Virginia DOT, Transportation and Mobility Planning 
jeremy.raw at vdot.virginia.gov / 804-786-0998

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf Of Albert-Jan Roskam
Sent: Tuesday, April 27, 2010 09:29 AM
To: R Mailing List
Subject: [R] sprintf() and return() oddity

Hi,
 
If I use sprintf and return inside a function, sprintf doesn't print anything anymore. See the non-sense example below.
 
> x <- function() { a <- 888
+ sprintf("xxx %s", a) }
> x()
[1] "xxx 888"
> x <- function() { a <- 888
+ sprintf("xxx %s", a) 
+ return(a) }
> x()
[1] 888

Is this a bug?

Cheers!!
Albert-Jan

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