# Re: [R] Flattening a list of data frames

From: Dimitris Rizopoulos <dimitris.rizopoulos_at_med.kuleuven.ac.be>
Date: Thu 10 Mar 2005 - 20:14:55 EST

try this:

do.call("rbind", z)

Best,
Dimitris

Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven

```Tel: +32/16/336899
Fax: +32/16/337015
Web: http://www.med.kuleuven.ac.be/biostat/
http://www.student.kuleuven.ac.be/~m0390867/dimitris.htm

```
• Original Message ----- From: "Lorin Hochstein" <lorin@cs.umd.edu> To: <R-help@stat.math.ethz.ch> Sent: Wednesday, March 09, 2005 9:07 PM Subject: [R] Flattening a list of data frames

> Hello all,
>
> Simple version of my problem:
>
> I've got a list of data frames, where each data frame has the same
> number of columns and the same column names. I'd like to flatten the
> list into one large data frame. Is there an easy way to do this?
>
> Quick example code:
> a <- data.frame(x=c(1,2,3),y=c(5,7,9)
> b <- data.frame(x=c(2,4,7,9),y=c(2,3,5,4))

> z <- list(a,b)
>
> # Do "something" to get the equivalent of rbind(z[],z[])
> ???
>
> More complex version:
>
> My data is in this format because it's the output of a "by" statment
> that looks like this:
>
> y <- by(d,list(d\$StudentID,d\$Assignment),gapfun)
>
> (where gapfun is a function I've defined that takes a data frame and
> returns another data frame).
>
> What I would like is to do is transform y into a data frame that has
> columns "StudentID", "Assignment", and the columns in the data frame
> returned by gapfun.
>
> Any ideas?
>
> Lorin
>
> ----------
> Lorin Hochstein
> Experimental Software Engineering Group
> Computer Science Department
> University of Maryland, College Park
>
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