# [R] loop with splitted data

Ling, Gary (Electronic Trading) Gary_Ling at ml.com
Wed Sep 10 18:08:11 CEST 2008

```YES! many many thanks, Jim.
I know it'd be simple, yet I can't believe it's that simple. =)

-gary

-----Original Message-----
From: jim holtman [mailto:jholtman at gmail.com]
Sent: Wednesday, September 10, 2008 11:55 AM
Cc: Peter Dalgaard; r-help at r-project.org
Subject: Re: [R] loop with splitted data

Is this what you want:

> lapply(z, '[[', 1)
[[1]]
[1] 1 2 3

[[2]]
[1] 11 12 13

> lapply(z, '[[', 2)
[[1]]
[1] 4 5 6

[[2]]
[1] 14 15 16

>

On Wed, Sep 10, 2008 at 11:43 AM, Ling, Gary (Electronic Trading)
<Gary_Ling at ml.com> wrote:
> Hi R users, I have a question which is some what related to this thread.
>
> Here is the setup:
> z is a list of lists, with no names.
> zz is same is z, but with names.
> with names on zz, I can crawl on the data with lapply, but I don't know how do the same on z (without names). Can someone help?
>
>
> ### === here is the code, which explains more clear of my problem
> x <- list(1:3,4:6)
> y <- list(11:13,14:16)
> z <- list(x,y)
>
> xx <- x
> names(xx) <- c("1","2")
> yy <- y
> names(yy) <- c("1","2")
> zz <- list(xx,yy)
>
> lapply(zz, "[[", "1")
> lapply(zz, "[[", "2")
> # Question: how can I get the same thing from z?
> # i.e. lapply(z, "[[", <???>), what is <???> so that
> # I can get the same values as lapply(zz, "[[", "1").
> # I tried <???>=[[1]], <???>=[1], <???>="[[". They all don't work.
> # I feel that I need a string or something to tell lapply what I want.
>
> This is a simplify version of my problem; in my case, I can't name all the sub-lists, please help.
>
> Gary
>
>
>
> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf Of Peter Dalgaard
> Sent: Tuesday, August 26, 2008 6:27 PM
> To: jim holtman
> Cc: r-help at r-project.org
> Subject: Re: [R] loop with splitted data
>
>
> jim holtman wrote:
>> Is this what you want:
>>
>>
>>> y = c(rep(2,5),rep(3,5))
>>> ma <- data.frame(x = 1:10, y=y  )
>>> splitted <- split(ma, ma\$y)
>>> for (counter in (min(ma\$y):max(ma\$y)))
>>>
>> + {
>> + cat(counter, ":", splitted[[as.character(counter)]]\$x, '\n')
>> + }
>> 2 : 1 2 3 4 5
>> 3 : 6 7 8 9 10
>>
>>
> But maybe this is what he really wanted:
>
>  > lapply(splitted,"[[", "x")
> \$`2`
> [1] 1 2 3 4 5
>
> \$`3`
> [1]  6  7  8  9 10
>
> or even
>
>  > split(ma\$x, ma\$y)
> \$`2`
> [1] 1 2 3 4 5
>
> \$`3`
> [1]  6  7  8  9 10
>
> --
>   O__  ---- Peter Dalgaard             Øster Farimagsgade 5, Entr.B
>  c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
>  (*) \(*) -- University of Copenhagen   Denmark      Ph:  (+45) 35327918
> ~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)              FAX: (+45) 35327907
>
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> and provide commented, minimal, self-contained, reproducible code.
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--
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?

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