# Re: [R] Splitting a set of vectors in a list (Solved )

From: Liaw, Andy <andy_liaw_at_merck.com>
Date: Fri, 14 Mar 2008 12:26:55 -0400

> ?"[" ?InternalMethods
>
> x[i,j] is just shorthand for "["(x,i,j) . (AFAIK)**All** operators
> (+,-,...,subscripting,...) in R are functions, stemming from
> its LISP-like
> heritage, and can actually called by the usual functional
> syntax, f(...),
> instead of the operator syntax.

That is true even for assignment:

R> "<-"(junk, 1:3)
R> junk
[1] 1 2 3

and "{":

R> "{"(1, 2, 3)
[1] 3

Andy

> Not sure where this is explicitly discussed within R's
> documentation, but
> you can find info on it in V&R's "S Programming", esp. p.24 and 4.3,
> "Extracting or replacing coefficients".
>
> No doubt, other S/R books explain it also.
>
> Cheers,
>
> Bert Gunter
> Genentech Nonclinical Statistics
> 47374
>
>
> -----Original Message-----
> From: r-help-bounces_at_r-project.org
> [mailto:r-help-bounces_at_r-project.org] On
> Behalf Of John Kane
> Sent: Thursday, March 13, 2008 11:53 AM
> To: Henrique Dallazuanna
> Cc: R R-help
> Subject: Re: [R] Splitting a set of vectors in a list (Solved )
>
> My thanks to Henrique Dallazuanna and Phil Spector.
> Both solutions worked well.
> Phil suggested that an alterative to my function would
> be
> vect1 = sapply(mylist,'[[',1)
> and I see that Henrique used `[` in his solution.
>
> Can you point me to some documentation that discusses
> these usages. I have seen them before but I have never
> actually figured out how to use them.?
>
> Thanks.
>
> Problem and solutions
> ========================================================
> mylist <- list(aa=c("cat","peach" ), bb=c("dog",
> "apple", "iron"),
> cc = c("rabbit", "orange", "zinc", "silk"))
> myfun <- function(dff) dff[1]
> vect1 <- unlist(lapply(mylist, myfun))
>
> # Desired output

> t(cbind( c("cat" , "peach" , NA, NA), bbb <- c("dog"
> , "apple" ,"iron", NA),
> ccb <- c("rabbit" ,"orange" ,"zinc" , "silk" )))
>
> # Phil Spector's approach
> mlen = max(sapply(mylist,length))
> eqlens = lapply(mylist,function(x)if(length(x) < mlen)
>
> c(x,rep('',mlen-length(x))) else x)
> do.call(rbind,eqlens)
>
> # "Henrique Dallazuanna" <wwwhsd_at_gmail.com>
> # I added the t()
> t(as.data.frame(lapply(mylist, `[`,
> 1:max(unlist(lapply(mylist,
> length))))))
>
>
> [[elided trailing spam]]
>
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> ______________________________________________
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> PLEASE do read the posting guide
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>
>
>

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