Re: [R] Dataframe manipulation

From: David Winsemius <dwinsemius_at_comcast.net>
Date: Tue, 4 Dec 2007 15:47:38 +0000 (UTC)

"Dimitris Rizopoulos" <dimitris.rizopoulos_at_med.kuleuven.be> wrote in news:002001c8367f$65a8d8d0$0540210a_at_www.domain:

> try this (also look at R-FAQ 7.10):
> 
> sapply(df, function (x) as.numeric(levels(x))[as.integer(x)])

That looks rather dangerous. By the time I saw your suggestion, I had already added an extra variable with:

df$testdata1<-as.numeric(levels(df$testdata))[as.integer(df$testdata)]  

When I tried your suggestion I got no error, but there was also no effect. When I tried:

df2<-sapply(df, function (x) as.numeric(levels(x))[as.integer(x)])

I discovered that the numeric variable, testdata1, had been entirely coverted to NA's and str(df2) did not look data.frame-like.

> is.data.frame(df2)
[1] FALSE

-- 
David Winsemius

> 
> ----- Original Message ----- 
> From: "Antje" <niederlein-rstat_at_yahoo.de>
> To: <r-help_at_stat.math.ethz.ch>
> Sent: Tuesday, December 04, 2007 11:46 AM
> Subject: [R] Dataframe manipulation
> 
> 

>> Hello,
>>
>> can anybody help me with this problem?
>> I have a dataframe, which contains its values as factors though I
>> have numbers
>> but it was read as factors with "scan". Now I would like to convert
>> these
>> columns (multiple) to a numeric format.
>>
>>
>> # this example creates a similar situation
>>
>> testdata <- as.factor(c("1.1",NA,"2.3","5.5"))
>> testdata2 <- as.factor(c("1.7","4.3","8.5",10.0))
>>
>> df <- data.frame(testdata, testdata2)
>>
>> what do I have to do to get the same datafram but with numeric
>> values???
>>
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Received on Tue 04 Dec 2007 - 16:00:10 GMT

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