[R] With an example - Re: rbind.data.frame drops attributes for factor variables

[David Winsemius]

On Nov 12, 2011, at 2:47 PM, Sammy Zee wrote:

> When I use rbind() or rbind.data.frame() to add a row to an existing
> dataframe, it appears that attributes for the column of type  
> "factor" are
> dropped. See the sample example below to reproduce the problem. Please
> suggest How I can fix this.
>

> Thanks,
> Sammy
>
> a=c("Male", "Male", "Female", "Male")
> b=c(1,2,3,4)
> c=c("great", "bad", "good", "bad")
> dataset<- data.frame (gender = a, count = b, answer = c)
>
>> dataset
>
> gender count answer
> 1   Male     1  great
> 2   Male     2    bad
> 3 Female     3   good
> 4   Male     4    bad
>
>
>> attributes(dataset$answer)
> $levels
> [1] "bad"   "good"  "great"
>
> $class
> [1] "factor"
>
> Now adding some custom attributes to column dataset$answer
>
> attributes(dataset$answer)<-c(attributes(dataset 
> $answer),list(newattr1="custom-attr1"))
> attributes(dataset$answer)<-c(attributes(dataset 
> $answer),list(newattr2="custom-attr2"))

If you look through the code of rbind.data.frame you see that column  
values are processed with the 'factor' function.

 > attributes(dataset$answer)
$levels
[1] "bad"   "good"  "great"

$class
[1] "factor"

$newattr1
[1] "custom-attr1"

$newattr2
[1] "custom-attr2"

 > attributes(factor(dataset$answer))
$levels
[1] "bad"   "good"  "great"

$class
[1] "factor"


So I think you are out of luck. You will need to restore the "special  
attributes" yourself.

-- 
David.
>
>> attributes(dataset$answer)
> $levels
> [1] "bad"   "good"  "great"
>
> $class
> [1] "factor"
>
> $newattr1
> [1] "custom-attr1"
>
> $newattr2
> [1] "custom-attr2"
>
> However as soon as I add a row to this data frame ("dataset") by  
> rbind(),
> it loses the custom
> attributes ("newattr1" and "newattr2") I have just added
>
> newrow = c(gender="Female", count = 5, answer = "great")
>
> dataset <- rbind(dataset, newrow)
>
>> attributes(dataset$answer)
> $levels
> [1] "bad"   "good"  "great"
>
> $class
> [1] "factor"
>
> the two custom attributes are dropped!! Any suggestion why this is
> happening.
>
> On Fri, Nov 11, 2011 at 11:44 AM, Jeff Newmiller
> <jdnewmil at dcn.davis.ca.us>wrote:
>
>> As the doctor says, if it hurts "don't do that".
>>
>> A factor is a sequence of integers with a corresponding list of  
>> character
>> strings. Factors in two separate vectors can and usually do map the  
>> same
>> integer to different strings, and R cannot tell how you want that  
>> resolved.
>>
>> Convert these columns to character before combining them, and only  
>> convert
>> to factor when you have all of your possibilities present (or you  
>> specify
>> them in the creation of the factor vector).
>> ---------------------------------------------------------------------------
>> Jeff Newmiller                        The     .....       .....  Go  
>> Live...
>> DCN:<jdnewmil at dcn.davis.ca.us>        Basics: ##.#.       ##.#.  Live
>> Go...
>>                                     Live:   OO#.. Dead: OO#..   
>> Playing
>> Research Engineer (Solar/Batteries            O.O#.       #.O#.  with
>> /Software/Embedded Controllers)               .OO#.       .OO#.   
>> rocks...1k
>> ---------------------------------------------------------------------------
>> Sent from my phone. Please excuse my brevity.
>>
>> Sammy Zee <szee2007 at gmail.com> wrote:
>>
>>> Hi all,
>>>
>>> When I use rbind() or rbind.data.frame() to add a row to an existing
>>> dataframe, it appears that attributes for the column of type  
>>> "factor"
>>> are
>>> dropped. I see the following post with same problem. However i did  
>>> not
>>> see
>>> any reply to the following posting offering a solution. Could  
>>> someone
>>> please help.
>>>
>>>
>> http://r.789695.n4.nabble.com/rbind-data-frame-drops-attributes-for-factor-variables-td919575.html
>>>
>>> Thanks,
>>> Sammy
>>>
>>>      [[alternative HTML version deleted]]
>>>
>>> ______________________________________________
>>> R-help at r-project.org mailing list
>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>> PLEASE do read the posting guide
>>> http://www.R-project.org/posting-guide.html
>>> and provide commented, minimal, self-contained, reproducible code.
>>
>>
>
> 	[[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

David Winsemius, MD
West Hartford, CT