[R] Change case of factor in data frame

[David Winsemius]

On Dec 3, 2012, at 3:34 PM, Audrey wrote:

>> res=names(dat);
>> get(res[ind],pos=dat) will retrieve dat$name
>
>
> There are far less baroque was of doing that (including dat$name and
> dat[["name"]].
>
> Both dat$name and dat[["name"]] require you to know what "name" is.  
> I was
> looking for a way to retrieve a data frame column by name without  
> actually
> knowing what the data frame column name was. get() seems to do that,  
> but I
> am open to other options.

And I gave you some, but you failed to include context, an annoying  
habit of Nabble users. (In my opinion the Nabble interface is more  
hassle than it is worth.)  For instance, I wrote:

>>
>> If you had a numeric object, 'ind' then
>>
>> dat[ind] would retrieve a sub-list, with as many columns as there  
>> were items in 'ind' and would have class data.frame.
>



>
> Thank you for your advice regarding [ vs. [[. Indeed,  
> lower(dat[[ind]]) does
> return the desired result. However, it seems that ind can only be a  
> single
> integer

That was what I wrote I believe.

> (or evaluate to TRUE for only 1 column),

In some instances TRUE is coerced to 1.

> I guess because "[[" is returning a vector.

No. You have failed to understand that "[[" can only return a single  
referenced object. It might be a vector or a list, but you cannot give  
it a vector with more than one element and expect satisfactory results.

>
> By "text" I mean anything that was non-numerical: character and factor
> classes, in my case.
>
Then you should be clear. "text" is not a well defined term when  
referring to R objects.

> View this message in context: http://r.789695.n4.nabble.com/Change-case-of-factor-in-data-frame-tp4651696p4651971.html
> Sent from the R help mailing list archive at Nabble.com.

No. This borders on actionable fraud.  R-help is not Nabble. Do not  
believe what Nabble is saying. Do read the Rhelp Posting Guide.



-- 

David Winsemius, MD
Alameda, CA, USA