[R] Assign a list to one column of data frame

[Bert Gunter]

Use list indexing, "[[" not "[" .

> df <- data.frame(a=1:3,b=letters[1:3])
> x <- "new"
> df[[x]]<-  I(list(1:5,g = "foo", abb = matrix(runif(6),nr=3)))
> df
  a b          new
1 1 a 1, 2, 3,....
2 2 b          foo
3 3 c 0.248115....
> df$new
[[1]]
[1] 1 2 3 4 5

$g
[1] "foo"

$abb
          [,1]      [,2]
[1,] 0.2481156 0.2138564
[2,] 0.8598658 0.2898058
[3,] 0.5854885 0.4084578


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 Sun, Dec 11, 2016 at 3:54 AM, Marlin JL.M <marlin- at gmx.cn> wrote:
>
> If you see my previous example, I have tried something like
>> df[,n3] <- I(mylist)
>
> However, in my case, the name of the new column is in a variable (by
> user input) which can not be directly used by the dollar assign. On the
> other hand, "[<-" does not work correctly even if I wrap the list into
> "I()".
>
> Perhaps the title of my email is a little unclear, sorry for the case.
>
> Best,
> Marlin.
>
> On Sun, 2016-12-11 at 03:03 -0800, Bert Gunter wrote:
>> ?data.frame says:
>>
>> "If a list or data frame or matrix is passed to data.frame it is as
>> if
>> each component or column had been passed as a separate argument
>> (except for matrices of class "model.matrix" and those protected by
>> I). "
>>
>> So doing what Help says to do seems to do what you asked:
>>
>>
>> > df <- data.frame(a=1:3,b=letters[1:3])
>> > df
>>
>>   a b
>> 1 1 a
>> 2 2 b
>> 3 3 c
>>
>> ## add a list column, protected by "I()"
>> > df$new <- I(list(1:5,g = "foo", abb = matrix(runif(6),nr=3)))
>>
>> ## works as advertised
>> > df
>>
>>   a b          new
>> 1 1 a 1, 2, 3,....
>> 2 2 b          foo
>> 3 3 c 0.080349....
>>
>> > df$new
>>
>> [[1]]
>> [1] 1 2 3 4 5
>>
>> $g
>> [1] "foo"
>>
>> $abb
>>            [,1]       [,2]
>> [1,] 0.08034915 0.83671591
>> [2,] 0.43938440 0.06067429
>> [3,] 0.88196881 0.33461234
>>
>>
>> Cheers,
>> Bert
>>
>>
>> Bert Gunter
>>
>> "The trouble with having an open mind is that people keep coming
>> along
>> and sticking things into it."
>> -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )
>>
>>
>> On Sat, Dec 10, 2016 at 7:18 PM, Marlin JL.M <marlin- at gmx.cn> wrote:
>> > Dear all,
>> >
>> > I want to assign a list to one column of data.frame where the name
>> > of the column
>> > is a variable. I tried the following:
>> >
>> > Using R version 3.3.2
>> >
>> > > df <- iris[1:3, ]
>> > > df
>> >
>> > # Sepal.Length Sepal.Width Petal.Length Petal.Width Species
>> > # 1          5.1         3.5          1.4         0.2  setosa
>> > # 2          4.9         3.0          1.4         0.2  setosa
>> > # 3          4.7         3.2          1.3         0.2  setosa
>> >
>> > > mylist <- list(c(1,2,3),c(1),c())
>> > > mylist
>> >
>> > # [[1]]
>> > # [1] 1 2 3
>> > #
>> > # [[2]]
>> > # [1] 1
>> > #
>> > # [[3]]
>> > # NULL
>> >
>> > > n1 <- 'new1'
>> > > df$n1 <- mylist
>> > > n2 <- 'new2'
>> > > df[,n2] <- mylist
>> >
>> > # Warning message:
>> > # In `[<-.data.frame`(`*tmp*`, , "new4", value = list(c(1, 2,
>> > 3),  :
>> > # provided 3 variables to replace 1 variables
>> >
>> > > n3 <- 'new3'
>> > > df[,n3] <- I(mylist)
>> >
>> > # Warning message:
>> > # In `[<-.data.frame`(`*tmp*`, , "new3", value = list(c(1, 2,
>> > 3),  :
>> > # provided 3 variables to replace 1 variables
>> >
>> > > eval(parse(text = paste0("df$","new4","<- mylist")))
>> > > df
>> >
>> > # Sepal.Length Sepal.Width Petal.Length Petal.Width Species      n1
>> > new2 new3    new4
>> > # 1          5.1         3.5          1.4         0.2  setosa 1, 2,
>> > 3    1    1 1, 2, 3
>> > #
>> > 2          4.9         3.0          1.4         0.2  setosa       1
>> >     2    2       1
>> > #
>> > 3          4.7         3.2          1.3         0.2  setosa    NULL
>> >     3    3    NULL
>> >
>> >
>> > The "eval" works correctly, however, if I want to avoid using
>> > "eval", what
>> > should I do?
>> >
>> > Thanks!
>> >
>> > ______________________________________________
>> > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
>> > https://stat.ethz.ch/mailman/listinfo/r-help
>> > PLEASE do read the posting guide http://www.R-project.org/posting-g
>> > uide.html
>> > and provide commented, minimal, self-contained, reproducible code.