[R] Converting a list to a data frame

[Jeff Newmiller]

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, "Tóth Dénes" <toth.denes using 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
>>
>
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-- 
Sent from my phone. Please excuse my brevity.