R, construct a data.frame column by using data from another list

Question

Given a list x:

$a
[1] 1 2 3 4 5 6
$b
[1] 10 20 30 40 50
$c
[1] 100 200 300 400 500

I want to construct a data frame that contains one column containing the following values:

1 10 100

Namely the elements of the column come from the first element in x$a, x$b and x$c.

I wonder what is the most efficient way to construct this column?

This can help you a little. [What is the most efficient way to cast a list as a data frame?](http://stackoverflow.com/questions/4512465/what-is-the-most-efficient-way-to-cast-a-list-as-a-data-frame) — Ronak Shah, Nov 01 '16 at 12:20

akrun · Accepted Answer · 2016-11-01T12:31:25.983

0

We can use [ to extract the 1st element

d1 <- data.frame(Col1 = unname(sapply(x, `[`, 1)))
d1
#   Col1
#1    1
#2   10
#3  100

We can also do

data.frame(Col1 = do.call(cbind, x)[1,])

edited Nov 01 '16 at 12:31

answered Nov 01 '16 at 12:17

akrun

score 0 · Answer 2 · answered Nov 01 '16 at 12:28

0

You can try this too:

data.frame(Col1=do.call(rbind, x)[,1])
  Col1
a    1
b   10
c  100

answered Nov 01 '16 at 12:28

Sandipan Dey

2 Answers2