[R] Column name containing "-"

[Bert Gunter]

Ivan:

On Tue, Jan 24, 2012 at 6:47 AM, Ivan Calandra
<ivan.calandra at u-bourgogne.fr> wrote:
> By "it works anyway", I mean that you can have a dash in a column name,
> there is no error or even warning.
> I guess that some functions would throw an error or warning, depending on
> the requirements, but data.frame() doesn't.

This is false. Please don't guess. Read the Help pages.

> data.frame(a = 1:3)  #fine
> data.frame(a-3 = 1:3) # Error: unexpected '=' in "data.frame(a-3 ="
The name in **NOT** OK. However,
> data.frame("a-3" = 1:3) # fine
  a.3
1   1
2   2
3   3

## A quoted  character string can be used as a column name
## The name will be changed to a legal name unless:

> data.frame("a-3" = 1:3,check.names=FALSE)
  a-3
1   1
2   2
3   3

However, as is obvious, there is much mischief possible from such
practices, so that they are best avoided.

-- Bert


>
> Ivan
>
> Le 24/01/12 15:35, David Winsemius a écrit :
>>
>>
>> On Jan 24, 2012, at 4:44 AM, Ivan Calandra wrote:
>>
>>> Hi Mark,
>>>
>>> I cannot tell you why (maybe someone else can), but the check.names
>>> argument to data.frame() interpret "a.-5" as an unvalid name and convert to
>>> to a valid one. What I don't understand is why it isn't "valid" since it
>>> works anyway.
>>
>>
>> The dash is not a valid character for column names. What do you mean by
>> "it works anyway"?
>>
>
> --
> Ivan CALANDRA
> Université de Bourgogne
> UMR CNRS/uB 6282 Biogéosciences
> 6 Boulevard Gabriel
> 21000 Dijon, FRANCE
> +33(0)3.80.39.63.06
> ivan.calandra at u-bourgogne.fr
>
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-- 

Bert Gunter
Genentech Nonclinical Biostatistics

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