R help - Apr 2009 - rbind data frames stored in a list

Hello everyone!

I have a list X with 3 elements, each of which is a data frame, for example:

a<-data.frame(a=1,b=2,c=3)
b<-data.frame(a=c(4,7),b=c(5,8),c=c(6,9))
c<-data.frame(a=c(10,13,16),b=c(11,14,17),c=c(12,15,18))
X<-list()
X[[1]]<-a
X[[2]]<-b
X[[3]]<-c
(X)

How can I most effectively transform X into a data frame with columns
a, b, and c?
I would love to find a generic solution, and not a specific solution
like this one:

frame<-rbind(X[[1]],X[[2]],X[[3]])

...because in reality I have a lot of elements of X.

Thank you very much!

-- 
Dimitri Liakhovitski
MarketTools, Inc.
Dimitri.Liakhovitski at markettools.com

On Apr 22, 2009, at 8:36 PM, Dimitri Liakhovitski wrote:
> Hello everyone!
>
> I have a list X with 3 elements, each of which is a data frame, for  
> example:
>
> a<-data.frame(a=1,b=2,c=3)
> b<-data.frame(a=c(4,7),b=c(5,8),c=c(6,9))
> c<-data.frame(a=c(10,13,16),b=c(11,14,17),c=c(12,15,18))
> X<-list()
> X[[1]]<-a
> X[[2]]<-b
> X[[3]]<-c
> (X)
>
> How can I most effectively transform X into a data frame with columns
> a, b, and c?
> I would love to find a generic solution, and not a specific solution
> like this one:
>
> frame<-rbind(X[[1]],X[[2]],X[[3]])
>
> ...because in reality I have a lot of elements of X.
>
> Thank you very much!
see ?do.call

 > do.call(rbind, X)
    a  b  c
1  1  2  3
2  4  5  6
3  7  8  9
4 10 11 12
5 13 14 15
6 16 17 18

HTH,

Marc Schwartz

?do.call

... as in do.call(rbind,X)

(A very useful and powerful feature os the S language: Computing on the
language. See V&R's "S Programming" for an informative
discussion (there may
well be others, of course).

 -- Bert

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
On
Behalf Of Dimitri Liakhovitski
Sent: Wednesday, April 22, 2009 6:36 PM
To: R-Help List
Subject: [R] rbind data frames stored in a list

Hello everyone!

I have a list X with 3 elements, each of which is a data frame, for example:

a<-data.frame(a=1,b=2,c=3)
b<-data.frame(a=c(4,7),b=c(5,8),c=c(6,9))
c<-data.frame(a=c(10,13,16),b=c(11,14,17),c=c(12,15,18))
X<-list()
X[[1]]<-a
X[[2]]<-b
X[[3]]<-c
(X)

How can I most effectively transform X into a data frame with columns
a, b, and c?
I would love to find a generic solution, and not a specific solution
like this one:

frame<-rbind(X[[1]],X[[2]],X[[3]])

...because in reality I have a lot of elements of X.

Thank you very much!

-- 
Dimitri Liakhovitski
MarketTools, Inc.
Dimitri.Liakhovitski at markettools.com

______________________________________________
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.

'do.call' is your friend::
> a<-data.frame(a=1,b=2,c=3)
> b<-data.frame(a=c(4,7),b=c(5,8),c=c(6,9))
> c<-data.frame(a=c(10,13,16),b=c(11,14,17),c=c(12,15,18))
> X<-list()
> X[[1]]<-a
> X[[2]]<-b
> X[[3]]<-c
> do.call(rbind, X)
   a  b  c
1  1  2  3
2  4  5  6
3  7  8  9
4 10 11 12
5 13 14 15
6 16 17 18


On Wed, Apr 22, 2009 at 9:36 PM, Dimitri Liakhovitski <ld7631 at
gmail.com> wrote:
> Hello everyone!
>
> I have a list X with 3 elements, each of which is a data frame, for
example:
>
> a<-data.frame(a=1,b=2,c=3)
> b<-data.frame(a=c(4,7),b=c(5,8),c=c(6,9))
> c<-data.frame(a=c(10,13,16),b=c(11,14,17),c=c(12,15,18))
> X<-list()
> X[[1]]<-a
> X[[2]]<-b
> X[[3]]<-c
> (X)
>
> How can I most effectively transform X into a data frame with columns
> a, b, and c?
> I would love to find a generic solution, and not a specific solution
> like this one:
>
> frame<-rbind(X[[1]],X[[2]],X[[3]])
>
> ...because in reality I have a lot of elements of X.
>
> Thank you very much!
>
> --
> Dimitri Liakhovitski
> MarketTools, Inc.
> Dimitri.Liakhovitski at markettools.com
>
> ______________________________________________
> 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.
>


-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?

Replying to my own post. I found the following solution:
full.frame<-as.data.frame(matrix(nrow=0,ncol=3))
names(full.frame)<-c("a","b","c")
for(j in 1:length(X)) {full.frame<-rbind(full.frame,X[[j]])}
(full.frame)

Is there a more elegant solution?
Thank you!
Dimitri



On Wed, Apr 22, 2009 at 9:36 PM, Dimitri Liakhovitski <ld7631 at
gmail.com> wrote:
> Hello everyone!
>
> I have a list X with 3 elements, each of which is a data frame, for
example:
>
> a<-data.frame(a=1,b=2,c=3)
> b<-data.frame(a=c(4,7),b=c(5,8),c=c(6,9))
> c<-data.frame(a=c(10,13,16),b=c(11,14,17),c=c(12,15,18))
> X<-list()
> X[[1]]<-a
> X[[2]]<-b
> X[[3]]<-c
> (X)
>
> How can I most effectively transform X into a data frame with columns
> a, b, and c?
> I would love to find a generic solution, and not a specific solution
> like this one:
>
> frame<-rbind(X[[1]],X[[2]],X[[3]])
>
> ...because in reality I have a lot of elements of X.
>
> Thank you very much!
>
> --
> Dimitri Liakhovitski
> MarketTools, Inc.
> Dimitri.Liakhovitski at markettools.com
>


-- 
Dimitri Liakhovitski
MarketTools, Inc.
Dimitri.Liakhovitski at markettools.com