[R] functions applied to two vectors

[Christos Hatzis]

> a <- c(2, 3, 7, 5)
> b <- c(4, 7, 8, 9)
> mapply(seq, from=a, to=b)

-Christos 

> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of Rolf Turner
> Sent: Tuesday, October 23, 2007 11:29 PM
> To: Anya Okhmatovskaia
> Cc: r-help at r-project.org
> Subject: Re: [R] functions applied to two vectors
> 
> 
> On 24/10/2007, at 4:15 PM, Anya Okhmatovskaia wrote:
> 
> > Hi,
> >
> > I am very new to R, so I apologize if I have missed some 
> trivial thing 
> > in the manuals/archives. I am trying to get rid of for loops in my 
> > code and replace them with R vector magic (with no success).
> >
> > Let's say I have 2 vectors of the same length:
> > a <- c(2, 3, 7, 5)
> > b <- c(4, 7, 8, 9)
> >
> > What I'd like to do is to generate a list(?) of 4 sequences using a 
> > [i] as a start indices, and b[i] as end indices:
> > 2,3,4
> > 3,4,5,6,7
> > 7,8
> > 5,6,7,8,9
> >
> > My first guess: "a:b", of course, does not work - only one sequence 
> > gets generated using the first values from both vectors, plus a 
> > warning.
> > Is there
> > a special syntax I can use to make ":" treat its operands 
> as vectors?
> > More generally, is there a standard way to apply some arbitrary 
> > functions to two or more vectors in an element-by-element 
> fashion? For 
> > instance,
> > sum(a,b)
> > will sum all values in both vectors; how can I make it produce a 
> > vector of pairwise sums instead?
> 
> Cute question!  The first idea that pops into my head is
> 
> 	apply(cbind(a,b),1,function(x){x[1]:x[2]})
> 
> This works --- but there may be better ideas.
> 
> 			cheers,
> 
> 				Rolf Turner
> 
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