[R] Adding List Elements To A Data Frame

[Bert Gunter]

Folks:

I think it worth noting that the solutions provided by Brian and
David, which look exactly the same when print()ed, are entirely
different beasts. Brian's gives a column of strings; David;s gives a
column of lists (a list of lists). str() will provide details.

Both solutions are "correct" -- and point out the dangers of posting a
poorly specified question without context. You get what you pay for. I
have no idea which, if either, is "correct". That depends entirely on
the unspecified use to which you wish to put the result.

Cheers,
Bert



On Fri, Jul 19, 2013 at 2:49 PM, Rui Barradas <ruipbarradas at sapo.pt> wrote:
> Hello,
>
> If you create the 3rd column like that, it will be named V3, not z. You must
> do one of
>
> myDataframe$z <- I(myList)
> myDataframe[["z"]] <- I(myList)
>
> Rui Barradas
>
> Em 19-07-2013 22:28, David Winsemius escreveu:
>>
>>
>> On Jul 19, 2013, at 12:54 PM, Pete Brecknock wrote:
>>
>>> Hi
>>>
>>> I am trying to add the contents of the list "myList" to a new column "z"
>>> in
>>> the data frame "myDataframe"
>>>
>>> myList <- list(c("A1","B1"), c("A2","B2","C2"), c("A3","B3"))
>>>
>>> myDataframe <- data.frame(x=c(1,2,3), y=c("R","S","T"))
>>>
>>> Would like to produce
>>>
>>> x  y  z
>>> 1  R  A1,B1
>>> 2  S  A2,B2,C2
>>> 3  T  A3,B3
>>>
>>> where z is a character string holding the contents of the different
>>> elements
>>> of the list.
>>
>>
>>> myDataframe[[3]] <- I(myList)
>>> myDataframe
>>
>>    x y          z
>> 1 1 R     A1, B1
>> 2 2 S A2, B2, C2
>> 3 3 T     A3, B3
>>
>
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-- 

Bert Gunter
Genentech Nonclinical Biostatistics

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