[R] Fwd: Extracting a particular column from list

[Eric Berger]

[Putting back onto r-help]

You could try sapply() and lapply().

> e <- sapply( 1:length(u), function(i) u[[i]][1] )
> e
# [1] "1" "a"    (note that the integer 1 became a character string "1")

> f <- lapply( 1:length(u), function(i) u[[i]][1] )
> f
[[1]]
[1] 1

[[2]]
[1] "a"

In this case sapply will try to create a vector, and all its elements will
need to be of the same type, so you end up with a character vector.
The second method returns a list, which may or may not be of use to you,
but each element of the list retains its type.



---------- Forwarded message ---------
From: Faheem Jan <faheemjan93 using yahoo.com>
Date: Thu, Jan 16, 2020 at 1:31 PM
Subject: Re: [R] Extracting a particular column from list
To: ericjberger using gmail.com <ericjberger using gmail.com>


In my problem i want to extract the first value of a and b and so on... So
using such data for further analysis

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On Thu, 16 Jan 2020 at 4:24 PM, Eric Berger
<ericjberger using gmail.com> wrote:
> u <- list(a=1:5, b=letters[1:3])
> u
# $a
# [1] 1 2 3 4 5
#
# $b
# [1] "a" "b" "c"
> u[["a"]]
[1] 1 2 3 4 5





On Thu, Jan 16, 2020 at 1:04 PM Faheem Jan via R-help <r-help using r-project.org>
wrote:

Hi. How to extract a column from the list.. I will be thanks full..

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