R help - Mar 2000 - Elementwise c() for lists

I have two lists of equal lengths. Each one consists of vectors. Is
there an elegant way to combine them elementwise? Elegant means: without
loops. 

For instance, for
> jja_list(1:3,4:7)
> jjb_list(rep(0,4),(2,5))
I would like to get:
> list(c(1:3,rep(0,4)),c(4:7,rep(2,5))).

   --- D.Trenkler ---

************************************************************************
*********
   Dietrich Trenkler
(trenkler at oec.uni-osnabrueck.de)      
   Statistik / Empirische Wirtschaftsforschung
   Universitaet Osnabrueck
   Rolandstrasse 8                             Phone: +49(0)
541-969-2753
   D-49069 Osnabrueck                        Fax  : +49(0) 541-969-2745
   GERMANY
************************************************************************
*********



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On Mon, 20 Mar 2000, Trenkler, Dietrich wrote:
> I have two lists of equal lengths. Each one consists of vectors. Is
> there an elegant way to combine them elementwise? Elegant means: without
> loops. 
> 
> For instance, for
> 
> > jja_list(1:3,4:7)
> > jjb_list(rep(0,4),(2,5))
> 
> I would like to get:
> 
> > list(c(1:3,rep(0,4)),c(4:7,rep(2,5))).

We are currently considering a 'lapplyAll' function that would be the
most
elegant solution to your problem (analogous to the LISP mapcar function).

For the time being

n<-length(list1)
sapply(1:n,function(i) c(list1[[i]],list2[[i]])

with an obvious generalisation to three or more lists.

It's not substantially faster than a for() loop, though.


Thomas Lumley
Assistant Professor, Biostatistics
University of Washington, Seattle

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