[R] Converting a list to a data frame

Wed May 2 23:43:52 CEST 2018

Typo: dat[[z]] should be x[[z]]:

x2 <- do.call(rbind, lapply(names(x), function(z) 
      data.frame(type=z, x[[z]])))
x2
  type x y
1    A 1 3
2    A 2 4
3    B 5 7
4    B 6 8

David C

-----Original Message-----
From: R-help <r-help-bounces using r-project.org> On Behalf Of David L Carlson
Sent: Wednesday, May 2, 2018 3:51 PM
To: William Dunlap <wdunlap using tibco.com>; Kevin E. Thorpe <kevin.thorpe using utoronto.ca>
Cc: r-help mailing list <r-help using r-project.org>
Subject: Re: [R] Converting a list to a data frame

Or add the type column first and then rbind:

x <- list(A=data.frame(x=1:2, y=3:4),B=data.frame(x=5:6,y=7:8))
x2 <- do.call(rbind, lapply(names(x), function(z) 
      data.frame(type=z, dat[[z]])))

----------------------------------------
David L Carlson
Department of Anthropology
Texas A&M University
College Station, TX 77843-4352

-----Original Message-----
From: R-help <r-help-bounces using r-project.org> On Behalf Of William Dunlap via R-help
Sent: Wednesday, May 2, 2018 12:28 PM
To: Kevin E. Thorpe <kevin.thorpe using utoronto.ca>
Cc: R Help Mailing List <r-help using r-project.org>
Subject: Re: [R] Converting a list to a data frame

> x1 <- do.call(rbind, c(x, list(make.row.names=FALSE)))
> x2 <- cbind(type=rep(names(x), vapply(x, nrow, 0)), x1)
> str(x2)
'data.frame':   4 obs. of  3 variables:
 $ type: Factor w/ 2 levels "A","B": 1 1 2 2
 $ x   : int  1 2 5 6
 $ y   : int  3 4 7 8

Bill Dunlap
TIBCO Software
wdunlap tibco.com

On Wed, May 2, 2018 at 10:11 AM, Kevin E. Thorpe <kevin.thorpe using utoronto.ca>
wrote:

> I suspect this is pretty easy, but I'm having trouble figuring it out.
> Basically, I have a list of data frames such as the following example:
>
> list(A=data.frame(x=1:2, y=3:4),B=data.frame(x=5:6,y=7:8))
>
> I would like to turn this into  data frame where the list elements are 
> essentially rbind'ed together and the element name becomes a new variable.
> For example, I would like to turn the list above into a data frame 
> that looks like this:
>
> data.frame(type=c("A","A","B","B"),x=c(1:2,5:6),y=c(3:4,7:8))
>
> Appreciate any pointers.
>
> Kevin
>
> --
> Kevin E. Thorpe
> Head of Biostatistics,  Applied Health Research Centre (AHRC) Li Ka 
> Shing Knowledge Institute of St. Michael's Hospital Assistant 
> Professor, Dalla Lana School of Public Health University of Toronto
> email: kevin.thorpe using utoronto.ca  Tel: 416.864.5776  Fax: 416.864.3016
>
> ______________________________________________
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