[R] [FORGED] same column name in a data frame

[David L Carlson]

How about just using data.frame(): instead of cbind():

> x <- data.frame(a=c(1,2,3))
> y <- data.frame(a=c(2,3,4))
> xy <- data.frame(x, y)
> str(xy)
'data.frame':   3 obs. of  2 variables:
 $ a  : num  1 2 3
 $ a.1: num  2 3 4
> xy$a
[1] 1 2 3
> xy$a.1
[1] 2 3 4

-------------------------------------
David L Carlson
Department of Anthropology
Texas A&M University
College Station, TX 77840-4352



-----Original Message-----
From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of peter dalgaard
Sent: Tuesday, March 14, 2017 8:43 AM
To: Rolf Turner <r.turner at auckland.ac.nz>
Cc: r-help at r-project.org
Subject: Re: [R] [FORGED] same column name in a data frame


> On 14 Mar 2017, at 03:43 , Rolf Turner <r.turner at auckland.ac.nz> wrote:
> 
> On 14/03/17 14:56, Jinsong Zhao wrote:
>> Hi there,
>> 
>> I happened to find the following code can generate a data frame with
>> same column name.
>> 
>>> x <- data.frame(a=c(1,2,3))
>>> y <- data.frame(a=c(2,3,4))
>>> z <- cbind(x,y)
>> 
>> However, in this case, one can not use the $ to extract the second
>> column, right?
>> 
>> Is it possible to prevent the cbind() produce a data frame with same
>> column name?
> 
> No.
> 
> Why not either:
> 
> (a) Just make sure the names in "x" and "y" differ?
> 
> Or:
> 
> (b) Change the names of "z", e.g. names(z) <- c("clyde","irving")?
> 
> Or maybe names(z) <- make.unique(names(z)).
> 
> You could probably write a wrapper function for cbind() to automate (b) if you really want to.
> 

Yes, this is what it is, and I doubt anyone is likely to set out to change it. 

However, it is a bit of an oddity compared to the (often undesirable) pains the data.frame code goes through to ensure distinct _row_ names; e.g.,

> cbind(data.frame(a=1), data.frame(a=2))
  a a
1 1 2

but 

> rbind(data.frame(a=c(foo=1)), data.frame(a=c(foo=2)))
     a
foo  1
foo1 2

-pr


-- 
Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Office: A 4.23
Email: pd.mes at cbs.dk  Priv: PDalgd at gmail.com

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