R help - Sep 2010 - efficient list indexing

Hello everyone,

I need some help with lists inside lists (a good way to emulate a struct)\

Assume that there is a small list called fred:
fred <- list(happy = 1:10, name = "squash")


and a big list called bigfred that includes fred list 5 times
bigfred <- rep(fred,5)

Is it possible somehow to index all these sublists(fred) inside bigfred with a 
more direct way like this:
bigfred[1] shows the first sublist fred
bigfred[2][2] shows the second sublist fred, the second element of the fred list

So far I found some way to do this by refering to the sublists by the following:
bigfred[1+index*length(fred)]
where index shows the beginning of a sublist.

I would like to thank you in advance for your help
Best Regards
Alex



      
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I'm confused by what you are looking for.
There's some slight possibility that you
are looking for double bracket subscripting
with a vector:

 > list(a=1:5, b=letters)[[c(2,4)]]
[1] "d"


On 22/09/2010 10:58, Alaios wrote:
> Hello everyone,
>
> I need some help with lists inside lists (a good way to emulate a struct)\
>
> Assume that there is a small list called fred:
> fred<- list(happy = 1:10, name = "squash")
>
>
> and a big list called bigfred that includes fred list 5 times
> bigfred<- rep(fred,5)
>
> Is it possible somehow to index all these sublists(fred) inside bigfred
with a
> more direct way like this:
> bigfred[1] shows the first sublist fred
> bigfred[2][2] shows the second sublist fred, the second element of the fred
list
>
> So far I found some way to do this by refering to the sublists by the
following:
> bigfred[1+index*length(fred)]
> where index shows the beginning of a sublist.
>
> I would like to thank you in advance for your help
> Best Regards
> Alex
>
>
>
>
> 	[[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org 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.
>
-- 
Patrick Burns
pburns at pburns.seanet.com
http://www.burns-stat.com
(home of 'Some hints for the R beginner'
and 'The R Inferno')

Hi:

I believe we had this discussion yesterday,
http://r.789695.n4.nabble.com/Object-oriented-programming-in-R-td2538541.html#a2538916

but since you chose to repeat that message, it clearly wasn't enough, so
start with

http://cran.r-project.org/doc/manuals/R-intro.html#Lists
http://stackoverflow.com/questions/2050790/how-to-correctly-use-lists-in-r

With the following example as a reference:
Empl <- list(employee = "Anna", spouse = "Fred", children
= 3,
            child.ages = c(4, 7, 9))

we quote Venables and Ripley (2002, p. 45):
  "It is important to appreciate the difference between [ and [[. The [
form
extracts sub-vectors, so Empl[2] is a list of length one, whereas Empl[[2]]
is a component (a character vector of length one)."

In that context, consider the following:
> Empl$employee
[1] "Anna"
> Empl$child.ages[2]
[1] 7
> x <- "spouse"; Empl[[x]]
[1] "Fred"
> Empl[[3]]
[1] 3
> Empl[[4]]
[1] 4 7 9
> Empl[[4]][2]
[1] 7
> Empl[4]
$child.ages
[1] 4 7 9
> Empl[4][2]   # Why?
$<NA>
NULL
> Empl[2]
$spouse
[1] "Fred"
> Empl[[2]]   # Why the difference?
[1] "Fred"


A somewhat more expansive discussion is found on pp. 12-13 of Venables and
Ripley (2000), S Programming.

Dennis

On Wed, Sep 22, 2010 at 2:58 AM, Alaios <alaios@yahoo.com> wrote:
> Hello everyone,
>
> I need some help with lists inside lists (a good way to emulate a struct)\
>
> Assume that there is a small list called fred:
> fred <- list(happy = 1:10, name = "squash")
>
>
> and a big list called bigfred that includes fred list 5 times
> bigfred <- rep(fred,5)
>
> Is it possible somehow to index all these sublists(fred) inside bigfred
> with a
> more direct way like this:
> bigfred[1] shows the first sublist fred
> bigfred[2][2] shows the second sublist fred, the second element of the fred
> list
>
> So far I found some way to do this by refering to the sublists by the
> following:
> bigfred[1+index*length(fred)]
> where index shows the beginning of a sublist.
>
> I would like to thank you in advance for your help
> Best Regards
> Alex
>
>
>
>
>        [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help@r-project.org 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.
>
	[[alternative HTML version deleted]]