Note that
c(list(1,2,3), list(4, 5,6), list(7,8,9, 10))
is identical to
list(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
You want either
list(list(1,2,3), list(4,5,6), list(7,8,9,10)) # list of 3 lists of numeric
scalars
or
list(c(1,2,3), c(4,5,6), c(7,8,9,10)) # list of 3 numeric vectors
In any case, you need to wrap it in I() when passing it to data.frame so it
doesn't
get converted to columns of a data.frame. E.g.,
> df <- data.frame(name = c("a","b","c"),
+ type = c(1, 2, 3),
+ rtn = I( list(c(1,2,3), c(4,5,6), c(7,8,9,10)) ))
> df[2, "rtn"]
[[1]]
[1] 4 5 6
> df[[2, "rtn"]]
[1] 4 5 6
> df
name type rtn
1 a 1 1, 2, 3
2 b 2 4, 5, 6
3 c 3 7, 8, 9, 10
Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com
> -----Original Message-----
> From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On
> Behalf
> Of Kevin Zembower
> Sent: Friday, March 08, 2013 4:49 PM
> To: r-help@r-project.org
> Subject: [R] data.frame with variable-length list
>
> Hello,
>
> I'm trying to create a data frame with three columns, one of which is a
> variable-length list. I tried:
>
> df <- data.frame(name = c("a", "b", "c"),
> type=c(1, 2, 3),
> rtn = c(list(1,2,3), list(4, 5,6), list(7,8,9, 10)
> )
> )
>
> This would be useful, for example, if the 'rtn' is a variable number of
> observations.
>
> That gave me:
> > df
> name type rtn.1 rtn.2 rtn.3 rtn.4 rtn.5 rtn.6 rtn.7 rtn.8 rtn.9 rtn.10
> 1 a 1 1 2 3 4 5 6 7 8 9 10
> 2 b 2 1 2 3 4 5 6 7 8 9 10
> 3 c 3 1 2 3 4 5 6 7 8 9 10
>
> What I wanted is something like this, conceptually:
> > df
> name type rtn
> 1 a 1 list(1, 2, 3)
> 2 b 2 list(4, 5, 6)
> 3 c 3 list(7, 8, 9, 10)
>
> I discovered this in the R Language Definition manual:
>
> "A data frame can contain a list that is the same length as the other
> components. The list can contain elements of differing lengths thereby
> providing a data structure for ragged arrays. However, as of this
> writing such arrays are not generally handled correctly. (2.3.2)"
>
> Is this still the case? What does 'not handled correctly' mean? Can I do
> something like:
>
> sample(df$rtn, 1)
>
> If this isn't the way to do this, can you suggest the correct way?
>
> Thanks for your help and advice.
>
> -Kevin
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
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