R help - Aug 2006 - How to iteratively extract elements out of a list

Dear List,

The following code produces a list, which is what I what:

set.seed(123)
tmpf <- function() {
x <- rpois(rpois(1,4),2)
}
n <- 3
m <- replicate(n,tmpf())
m

[[1]]
[1] 3 2 4

[[2]]
[1] 0 2 4 2 2 5 2

[[3]]
[1] 2 0 4 1 0


Now I need something that would to extract iteratively (or as many
times as
the size of 'n') the values that are greater than 2 in each component
of
'm' into another list such that the sub-list would be:

[[1]]
[1] 3 4

[[2]]
[1] 4 5

[[3]]
[1] 4

Below is what I tried:

for(i in 1:3)
sub.list <- lapply(m,subset,m[[i]]>2)
> sub.list
which gives me something different from what I want:

[[1]]
[1] 4

[[2]]
[1] 4

[[3]]
[1] 4

Any help would be appreciated.
> version
         _
platform i386-pc-mingw32
arch     i386
os       mingw32
system   i386, mingw32
status
major    2
minor    2.1
year     2005
month    12
day      20
svn rev  36812
language R

try this:
> set.seed(123)
> tmpf <- function() {
+ x <- rpois(rpois(1,4),2)
+ }
> n <- 3
> m <- replicate(n,tmpf())
> m
[[1]]
[1] 3 2 4

[[2]]
[1] 0 2 4 2 2 5 2

[[3]]
[1] 2 0 4 1 0
> lapply(m, function(x)x[x>2])
[[1]]
[1] 3 4

[[2]]
[1] 4 5

[[3]]
[1] 4
>
On 8/25/06, xpRt.wannabe <xprt.wannabe at gmail.com>
wrote:
> Dear List,
>
> The following code produces a list, which is what I what:
>
> set.seed(123)
> tmpf <- function() {
> x <- rpois(rpois(1,4),2)
> }
> n <- 3
> m <- replicate(n,tmpf())
> m
>
> [[1]]
> [1] 3 2 4
>
> [[2]]
> [1] 0 2 4 2 2 5 2
>
> [[3]]
> [1] 2 0 4 1 0
>
>
> Now I need something that would to extract iteratively (or as many
> times as
> the size of 'n') the values that are greater than 2 in each
component
> of
> 'm' into another list such that the sub-list would be:
>
> [[1]]
> [1] 3 4
>
> [[2]]
> [1] 4 5
>
> [[3]]
> [1] 4
>
> Below is what I tried:
>
> for(i in 1:3)
> sub.list <- lapply(m,subset,m[[i]]>2)
>
> > sub.list
>
> which gives me something different from what I want:
>
> [[1]]
> [1] 4
>
> [[2]]
> [1] 4
>
> [[3]]
> [1] 4
>
> Any help would be appreciated.
>
> > version
>         _
> platform i386-pc-mingw32
> arch     i386
> os       mingw32
> system   i386, mingw32
> status
> major    2
> minor    2.1
> year     2005
> month    12
> day      20
> svn rev  36812
> language R
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem you are trying to solve?

lapply(m,function(x)x[x>2])
[[1]]
[1] 3 4

[[2]]
[1] 4 5

[[3]]
[1] 4

On 8/26/06, Patrick Connolly <p_connolly at ihug.co.nz>
wrote:
> On Sat, 26-Aug-2006 at 09:57AM +0100, Patrick Burns wrote:
>
> |>  > sub.m <- lapply(m, function(x)x[x>2])
> |>  > sub.m
> |> [[1]]
> |> [1] 3 4
> |>
> |> [[2]]
> |> [1] 4 5
> |>
> |> [[3]]
> |> [1] 4
> |>
> |>  > sub.m[unlist(lapply(sub.m, function(x) length(x) == 2))]
> |> [[1]]
> |> [1] 3 4
> |>
> |> [[2]]
> |> [1] 4 5
> |>
> |>  > sub4.m <- lapply(m, function(x)x[x>4])
> |>  > sub4.m[unlist(lapply(sub4.m, function(x) length(x) > 0))]
> |> [[1]]
> |> [1] 5
>
> Or slightly shorter in this case:
>
> sub.m[sapply(sub.m, function(x) length(x) == 2)]
>
or even shorter:

sub.m[sapply(sub.m, length) == 2]

Hi

try to do it without loop

lapply(m,function(x) x[x>2])

HTH
Petr


On 25 Aug 2006 at 13:52, xpRt.wannabe wrote:

Date sent:      	Fri, 25 Aug 2006 13:52:51 -0500
From:           	"xpRt.wannabe" <xprt.wannabe at gmail.com>
To:             	r-help at stat.math.ethz.ch
Subject:        	[R] How to iteratively extract elements out of a list
> Dear List,
> 
> The following code produces a list, which is what I what:
> 
> set.seed(123)
> tmpf <- function() {
> x <- rpois(rpois(1,4),2)
> }
> n <- 3
> m <- replicate(n,tmpf())
> m
> 
> [[1]]
> [1] 3 2 4
> 
> [[2]]
> [1] 0 2 4 2 2 5 2
> 
> [[3]]
> [1] 2 0 4 1 0
> 
> 
> Now I need something that would to extract iteratively (or as many
> times as the size of 'n') the values that are greater than 2 in
each
> component of 'm' into another list such that the sub-list would be:
> 
> [[1]]
> [1] 3 4
> 
> [[2]]
> [1] 4 5
> 
> [[3]]
> [1] 4
> 
> Below is what I tried:
> 
> for(i in 1:3)
> sub.list <- lapply(m,subset,m[[i]]>2)
> 
> > sub.list
> 
> which gives me something different from what I want:
> 
> [[1]]
> [1] 4
> 
> [[2]]
> [1] 4
> 
> [[3]]
> [1] 4
> 
> Any help would be appreciated.
> 
> > version
>          _
> platform i386-pc-mingw32
> arch     i386
> os       mingw32
> system   i386, mingw32
> status
> major    2
> minor    2.1
> year     2005
> month    12
> day      20
> svn rev  36812
> language R
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html and provide commented,
> minimal, self-contained, reproducible code.
Petr Pikal
petr.pikal at precheza.cz