[Rd] round() ignores missing arguments if it is used inside another function where some arguments are missing.

[Simon Urbanek]

On Nov 18, 2011, at 10:43 AM, Joris Meys wrote:

> I have stumbled across some behaviour in R that I really can't place,
> and that makes coding a bit tricky. I know that I can work around it
> when explicitly checking for missing arguments, but still...
> I have two functions. I have a first function based on paste
> 
>     fun1 <- function(x,y){
>       print(missing(y))
>       paste(x,'X',sep=y)
>     }
> 
> If I try this function without specifying `y`, I get the (expected)
> error message:
> 
>     > fun1(letters[1:6])
>     [1] TRUE
>     Error in paste(x, "X", sep = y) :
>       argument "y" is missing, with no default
> 
> The second one with round :
>     fun2 <- function(x,y){      print(missing(y))      round(x,digits=y)    }
> If I try this function without specifying `y`, it works unexpectedly
> whereas it shouldn't :
>     > fun2(100.1)    [1] TRUE    [1] 100
> In my view, fun1 should definitely give the error message as well, as
> it is not intended to have a default behaviour when y is missing.
> Still, the round() function ignores the fact y is missing. Is this by
> design, is there a check missing in round, or is something else going
> on that I am overlooking?
> 

> round
function (x, digits = 0)  .Primitive("round")

it has a default so it is fine for digits to be missing since it will have value 0 in that case ...

Cheers,
S


> Cheers
> Joris
>> sessionInfo()
> R version 2.14.0 (2011-10-31)
> Platform: i386-pc-mingw32/i386 (32-bit)
> 
> locale:
> [1] LC_COLLATE=English_United Kingdom.1252
> [2] LC_CTYPE=English_United Kingdom.1252
> [3] LC_MONETARY=English_United Kingdom.1252
> [4] LC_NUMERIC=C
> [5] LC_TIME=English_United Kingdom.1252
> 
> attached base packages:
> [1] stats     graphics  grDevices utils     datasets  methods
> [7] base
> 
> loaded via a namespace (and not attached):
> [1] tools_2.14.0
> 
> -- 
> Joris Meys
> Statistical consultant
> 
> Ghent University
> Faculty of Bioscience Engineering
> Department of Mathematical Modelling, Statistics and Bio-Informatics
> 
> tel : +32 9 264 59 87
> Joris.Meys at Ugent.be
> -------------------------------
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> 
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