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

dataset[ nrow(dataset), ] <- c ("Male", 5, "bad")

The above seems to have worked to append a row in place of a rbind(). 

method does not drop the custom attributes from the column. Do yo see 

issue with this method.

Thanks,
Sammy

On Sat, Nov 12, 2011 at 10:16 PM, David Winsemius 

On Nov 12, 2011, at 6:40 PM, Sammy Zee wrote:

 Thanks David. Besides rbind(), is there any other way to add a row to 

data frame so that I do not lose the custom attributes.

I have already told you the method that I know of. You don't seem to 

taken my poin that it is not a data.frame specific problem but rahter 

facor problem. You are welcome to redefine `rbind.data.frame`. The R
language is rather flexible in that manner.

--
David.

Thanks,
Sammy

On Sat, Nov 12, 2011 at 5:17 PM, David Winsemius 

wrote:

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" 

dropped. See the sample example below to reproduce the problem. 

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 

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 

strings. Factors in two separate vectors can and usually do map the 

integer to different strings, and R cannot tell how you want that
resolved.

Convert these columns to character before combining them, and only 

to factor when you have all of your possibilities present (or you 

them in the creation of the factor vector).
------------------------------**------------------------------**
---------------
Jeff Newmiller                        The     .....       .....  Go
Live...

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 

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<http://r.

789695.n4.nabble.com/rbind-data-frame-drops-attributes-for-factor-
variables-td919575.html>

Thanks,
Sammy

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___

David Winsemius, MD
West Hartford, CT

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