[Rd] cbind error with check.names

[Ista Zahn]

On Tue, Jul 23, 2013 at 12:54 PM, Fg Nu <fgnu32 at yahoo.com> wrote:
>
>
>
> ----- Original Message -----
> From: Ista Zahn <istazahn at gmail.com>
> To: Fg Nu <fgnu32 at yahoo.com>
> Cc: "r-devel at r-project.org" <r-devel at r-project.org>
> Sent: Tuesday, July 23, 2013 9:50 PM
> Subject: Re: [Rd] cbind error with check.names
>
> On Tue, Jul 23, 2013 at 9:18 AM, Fg Nu <fgnu32 at yahoo.com> wrote:
>>
>>
>>
>> Here is an example where cbind fails with an error when check.names=TRUE is set.
>>
>> data(airquality)
>> airQualityBind =cbind(airquality,airquality,check.names =TRUE)
>>
>>
>>  I understand that cbind is a call to data.frame and the following works:
>> airQualityBind =data.frame(airquality,airquality,check.names =TRUE)
>> but I would like to understand why cbind throws an error.
>>
>> I asked this question on SO here:
>> http://stackoverflow.com/questions/17810470/cbind-error-with-check-names
>> and user Hong Ooi confirmed my suspicion that cbind was passing check.names = FALSE regardless of my setting that option, even though the help file indicates that this should be possible,
>>
>> "For the "data.frame" method of cbind these can be further arguments to data.frame such as stringsAsFactors."
>>
>> Is there some design principle that I am missing here?
>
>
> Well, the function does work as documented. See the help file section
> on "Data frame methods", which says "The 'cbind' data frame method is
> just a wrapper for 'data.frame(..., check.names = FALSE)'".
>
> Best,
> Ista
>
>
>
> Is there then a reason that overriding the check.names default is forbidden from cbind? I can't tell why this would be the case.

For the same reason you can't have

data.frame(x=1:10, x=11:20, check.names=TRUE, check.names=FALSE)

or

mean(x=1:10, x=11:20)

i.e, you can't generally pass the same argument more than once. There
are exceptions to this, e.g.,

sum(c(NA, 1:10), na.rm=TRUE, na.rm=FALSE)

but in general each argument can only be matched once. Since
cbind.data.frame calls data.frame with check.names=FALSE, you can't
supply it again.

Best,
Ista

>
> Thanks
>