[R] loop with splitted data

[Ling, Gary (Electronic Trading)]

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.

Thanks in advance,
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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