Converting a list to a data frame

This is very nice to learn about, Denis, but it seems only fair to point out that the result of rbindlist is not a data frame.  You can convert it to a data frame easily, but the copy and indexing semantics of data tables are quite different than data tables, which could be a real headache for someone not prepared for those differences. (To learn more, read the data tables vignette.)

Tibbles  (as produced by unnest in my previous response) are not data tables either, but they behave much more like data frames than data tables do.

On May 2, 2018 1:30:37 PM MDT, "T?th D?nes" <toth.denes at kogentum.hu> wrote:

On 05/02/2018 07:11 PM, Kevin E. Thorpe 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.

Hi Kevin,

data.table::rbindlist does exactly what you want in a very efficient
way:

library(data.table)
dat <- list(A=data.frame(x=1:2, y=3:4),B=data.frame(x=5:6,y=7:8))
rbindlist(dat, idcol = "type")

Regards,
Denes

Kevin