R help - Apr 2013 - Transformation of a variable in a dataframe

HI,
   I have a dataframe with two variable A, B. I transform the two variable
and name them as C, D and save it in a dataframe  dfcd. However, I wonder
why can't I call them by dfcd$C and dfcd$D?

   Thanks,

Miao
> A=c(1,2,3)
> B=c(4,6,7)
> dfab<-data.frame(A,B)
> C=dfab["A"]*2
> D=dfab["B"]*3
> dfcd<-data.frame(C,D)
> dfcd
  A  B
1 2 12
2 4 18
3 6 21
> dfcd$C
NULL
> dfcd$A
[1] 2 4 6

	[[alternative HTML version deleted]]

Hi,

Because a column name exists for "C" and "D":

 > colnames(C)
[1] "A"
 > colnames(D)
[1] "B"

One possibility:
 > A=c(1,2,3)
 > B=c(4,6,7)
 > dfab<-data.frame(A,B)
 > C=dfab$A*2
 > D=dfab$B*3
 > dfcd<-data.frame(C,D)
 > dfcd
   C  D
1 2 12
2 4 18
3 6 21
 > dfcd$C
[1] 2 4 6

HTH,
Pascal


On 04/17/2013 02:33 PM, jpm miao wrote:
> HI,
>     I have a dataframe with two variable A, B. I transform the two variable
> and name them as C, D and save it in a dataframe  dfcd. However, I wonder
> why can't I call them by dfcd$C and dfcd$D?
>
>     Thanks,
>
> Miao
>
>> A=c(1,2,3)
>> B=c(4,6,7)
>> dfab<-data.frame(A,B)
>> C=dfab["A"]*2
>> D=dfab["B"]*3
>> dfcd<-data.frame(C,D)
>> dfcd
>    A  B
> 1 2 12
> 2 4 18
> 3 6 21
>> dfcd$C
> NULL
>> dfcd$A
> [1] 2 4 6
>
> 	[[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.
>

On Apr 16, 2013, at 10:33 PM, jpm miao wrote:
> HI,
>   I have a dataframe with two variable A, B. I transform the two  
> variable
> and name them as C, D and save it in a dataframe  dfcd. However, I  
> wonder
> why can't I call them by dfcd$C and dfcd$D?
Because you didn't assign them to dfab$C. It's going to be more  
successful if you use:

dfab[["A"]]*2
>
>   Thanks,
>
> Miao
>
>> A=c(1,2,3)
>> B=c(4,6,7)
>> dfab<-data.frame(A,B)
>> C=dfab["A"]*2
>> D=dfab["B"]*3
>> dfcd<-data.frame(C,D)
>> dfcd
>  A  B
> 1 2 12
> 2 4 18
> 3 6 21
>> dfcd$C
> NULL
>> dfcd$A
> [1] 2 4 6
>
> 	[[alternative HTML version deleted]]

David Winsemius, MD
Alameda, CA, USA

Hi,

You may also try:

dfab<-data.frame(A,B)
library(plyr)
?dfcd<-subset(mutate(dfab,C=A*2,D=B*3),select=-c(A,B))
#or
?dfcd1<-subset(within(dfab,{D<-B*3;C<-A*2}),select=-c(A,B))
dfcd$C
#[1] 2 4 6
?dfcd$D
#[1] 12 18 21
A.K.



----- Original Message -----
From: jpm miao <miaojpm at gmail.com>
To: r-help <r-help at r-project.org>
Cc: 
Sent: Wednesday, April 17, 2013 1:33 AM
Subject: [R] Transformation of a variable in a dataframe

HI,
?  I have a dataframe with two variable A, B. I transform the two variable
and name them as C, D and save it in a dataframe? dfcd. However, I wonder
why can't I call them by dfcd$C and dfcd$D?

?  Thanks,

Miao
> A=c(1,2,3)
> B=c(4,6,7)
> dfab<-data.frame(A,B)
> C=dfab["A"]*2
> D=dfab["B"]*3
> dfcd<-data.frame(C,D)
> dfcd
? A? B
1 2 12
2 4 18
3 6 21
> dfcd$C
NULL
> dfcd$A
[1] 2 4 6

??? [[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.