R help - Feb 2011 - converting the string columns in a data.frame to factors?

Dear All,

I'm not sure if I understand the parameter stringsAsFactors correctly.
I'm
trying to convert the string columns in aframe1 to factors. But it
seems stringsAsFactors=T in as.data.frame() doesn't do anything. Could
anybody let know what is the correct way to converting strings to factors?
> aframe1=data.frame(x=LETTERS[1:10], y=LETTERS[1:10], stringsAsFactors=F)
> aframe2=as.data.frame(aframe1, stringsAsFactors=T)
>
> str(aframe1)
'data.frame': 10 obs. of  2 variables:
 $ x: chr  "A" "B" "C" "D" ...
 $ y: chr  "A" "B" "C" "D"
...
> str(aframe2)
'data.frame': 10 obs. of  2 variables:
 $ x: chr  "A" "B" "C" "D" ...
 $ y: chr  "A" "B" "C" "D"
...
>
Thanks,
John

	[[alternative HTML version deleted]]

Hi John,

Use factor():
aframe2$x <- factor(aframe2$x)

Or, for all columns at once (there might be an easier solution):
aframe2 <- as.data.frame(lapply(aframe1, factor))

see ?factor

HTH,
Ivan

Le 2/28/2011 18:13, John Edwards a ?crit :
> Dear All,
>
> I'm not sure if I understand the parameter stringsAsFactors correctly.
I'm
> trying to convert the string columns in aframe1 to factors. But it
> seems stringsAsFactors=T in as.data.frame() doesn't do anything. Could
> anybody let know what is the correct way to converting strings to factors?
>
>> aframe1=data.frame(x=LETTERS[1:10], y=LETTERS[1:10],
stringsAsFactors=F)
>> aframe2=as.data.frame(aframe1, stringsAsFactors=T)
>>
>> str(aframe1)
> 'data.frame': 10 obs. of  2 variables:
>   $ x: chr  "A" "B" "C" "D" ...
>   $ y: chr  "A" "B" "C" "D" ...
>> str(aframe2)
> 'data.frame': 10 obs. of  2 variables:
>   $ x: chr  "A" "B" "C" "D" ...
>   $ y: chr  "A" "B" "C" "D" ...
> Thanks,
> John
>
> 	[[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list
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> PLEASE do read the posting guide
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> and provide commented, minimal, self-contained, reproducible code.
>
-- 
Ivan CALANDRA
PhD Student
University of Hamburg
Biozentrum Grindel und Zoologisches Museum
Abt. S?ugetiere
Martin-Luther-King-Platz 3
D-20146 Hamburg, GERMANY
+49(0)40 42838 6231
ivan.calandra at uni-hamburg.de

**********
http://www.for771.uni-bonn.de
http://webapp5.rrz.uni-hamburg.de/mammals/eng/1525_8_1.php

John,

as.data.frame is a generic function that will call different methods
depending on what class of object you pass to it.  The different
methods may have different arguments that they expect or honor.

The stringsAsFactors parameter is only used in certain methods of
as.data.frame.  When you pass an actual data.frame to that function,
stringsAsFactors is not used.  It looks like it is only used for
methods for character and matrix objects.

So, to do what you want:

aframe1 <- data.frame(x = LETTERS[1:10],
                       y = LETTERS[1:10],
                       z = 1:10,
                       stringsAsFactors = FALSE)

ind <- sapply(aframe1, is.character)
aframe1[ind] <- lapply(aframe1[ind], factor)

John Edwards wrote:
> Dear All,
> 
> I'm not sure if I understand the parameter stringsAsFactors correctly.
I'm
> trying to convert the string columns in aframe1 to factors. But it
> seems stringsAsFactors=T in as.data.frame() doesn't do anything. Could
> anybody let know what is the correct way to converting strings to factors?
> 
>> aframe1=data.frame(x=LETTERS[1:10], y=LETTERS[1:10],
stringsAsFactors=F)
>> aframe2=as.data.frame(aframe1, stringsAsFactors=T)
>>
>> str(aframe1)
> 'data.frame': 10 obs. of  2 variables:
>  $ x: chr  "A" "B" "C" "D" ...
>  $ y: chr  "A" "B" "C" "D" ...
>> str(aframe2)
> 'data.frame': 10 obs. of  2 variables:
>  $ x: chr  "A" "B" "C" "D" ...
>  $ y: chr  "A" "B" "C" "D" ...
> 
> Thanks,
> John
> 
> 	[[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.