I believe that a slightly more efficient way of doing this without
leaving base R is:
cbind(do.call(rbind,x), set = rep(seq_along(x), vapply(x,nrow,1)) )
Cheers,
Bert
Bert Gunter
"The trouble with having an open mind is that people keep coming along
and sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )
On Fri, Nov 4, 2016 at 5:50 AM, Charles Determan <cdeterma...@gmail.com> wrote:
> Hi Kevin,
>
> There may be a more elegant way but the following do.call and lapply should
> solve your problem.
>
> do.call(rbind, lapply(seq(length(x)), function(i) data.frame(set=i,
> x[[i]])))
>
> Regards,
> Charles
>
> On Fri, Nov 4, 2016 at 7:37 AM, Kevin E. Thorpe <kevin.tho...@utoronto.ca>
> wrote:
>
>> There is probably a very simple elegant way to do this, but I have been
>> unable to find it. Here is a toy example. Suppose I have a list of data
>> frames like this.
>>
>> print(x <- list('1'=data.frame(id=1:4,expand.grid(x1=0:1,x2=0:1)),'2'=
>> data.frame(id=5:8,expand.grid(x1=2:3,x2=2:3))))
>> $`1`
>> id x1 x2
>> 1 1 0 0
>> 2 2 1 0
>> 3 3 0 1
>> 4 4 1 1
>>
>> $`2`
>> id x1 x2
>> 1 5 2 2
>> 2 6 3 2
>> 3 7 2 3
>> 4 8 3 3
>>
>> The real application will have more than 2 elements so I'm looking for a
>> general approach. I basically want to rbind the data frames in each list
>> element and add a variable that adds the element name. In this example the
>> result would look something like this.
>>
>> rbind(data.frame(set='1',x[[1]]),data.frame(set='2',x[[2]]))
>> set id x1 x2
>> 1 1 1 0 0
>> 2 1 2 1 0
>> 3 1 3 0 1
>> 4 1 4 1 1
>> 5 2 5 2 2
>> 6 2 6 3 2
>> 7 2 7 2 3
>> 8 2 8 3 3
>>
>> Obviously, for 2 elements the simple rbind works but I would like a
>> general solution for arbitrary length lists. Hopefully that is clear.
>>
>> 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.tho...@utoronto.ca Tel: 416.864.5776 Fax: 416.864.3016
>>
>> ______________________________________________
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>> and provide commented, minimal, self-contained, reproducible code.
>>
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
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