Assign a list to one column of data frame

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

df$new

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!