Re: [R] converting the string columns in a data.frame to factors?

From: Erik Iverson <eriki_at_ccbr.umn.edu>
Date: Mon, 28 Feb 2011 11:25:27 -0600

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]]
>
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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. Received on Mon 28 Feb 2011 - 17:28:21 GMT

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