R help - Nov 2008 - construct a vector

Hi all,
I have an unkown number of vectors (>=2) all of the same length. Out
of these, I want to construct a new one as follows:
having vectors u,v and w, the resulting vector z should have entries:
z[1] = u[1], z[2] = v[1], z[3] = w[1]
z[4] = u[2], z[5] = v[2], z[6] = w[2]
...
i.e. go through the vector u,v,w, take at each time the 1st, 2sd, ...
elements and store them consecutively in z.
Is there an efficient way in R to do this?

Thanks in advance
Armin

on 11/26/2008 07:11 AM axionator wrote:
> Hi all,
> I have an unkown number of vectors (>=2) all of the same length. Out
> of these, I want to construct a new one as follows:
> having vectors u,v and w, the resulting vector z should have entries:
> z[1] = u[1], z[2] = v[1], z[3] = w[1]
> z[4] = u[2], z[5] = v[2], z[6] = w[2]
> ...
> i.e. go through the vector u,v,w, take at each time the 1st, 2sd, ...
> elements and store them consecutively in z.
> Is there an efficient way in R to do this?
> 
> Thanks in advance
> Armin
Is this what you want?

u <- 1:10
v <- 11:20
w <- 21:30

z <- as.vector(rbind(u, v, w))
> z
 [1]  1 11 21  2 12 22  3 13 23  4 14 24  5 15 25  6 16 26  7 17 27  8
[23] 18 28  9 19 29 10 20 30


Essentially, we are creating a matrix from the 3 vectors:
> rbind(u, v, w)
  [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
u    1    2    3    4    5    6    7    8    9    10
v   11   12   13   14   15   16   17   18   19    20
w   21   22   23   24   25   26   27   28   29    30

Then coercing that to a vector, taking advantage of the way in which
matrix elements are stored.

HTH,

Marc Schwartz

> I have an unkown number of vectors (>=2) all of the same length. Out
> of these, I want to construct a new one as follows:
> having vectors u,v and w, the resulting vector z should have entries:
> z[1] = u[1], z[2] = v[1], z[3] = w[1]
> z[4] = u[2], z[5] = v[2], z[6] = w[2]
> ...
> i.e. go through the vector u,v,w, take at each time the 1st, 2sd, ...
> elements and store them consecutively in z.
> Is there an efficient way in R to do this?
u <- 1:5
v <- (1:5) + 0.1
w <- (1:5) + 0.2
as.vector(rbind(u,v,w))
# [1] 1.0 1.1 1.2 2.0 2.1 2.2 3.0 3.1 3.2 4.0 4.1 4.2 5.0 5.1 5.2

Regards,
Richie.

Mathematical Sciences Unit
HSL


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axionator wrote:
> Hi all,
> I have an unkown number of vectors (>=2) all of the same length. Out
> of these, I want to construct a new one as follows:
> having vectors u,v and w, the resulting vector z should have entries:
> z[1] = u[1], z[2] = v[1], z[3] = w[1]
> z[4] = u[2], z[5] = v[2], z[6] = w[2]
> ...
> i.e. go through the vector u,v,w, take at each time the 1st, 2sd, ...
> elements and store them consecutively in z.
> Is there an efficient way in R to do this?
>
>   
suppose you have your vectors collected into a list, say vs; then the
following will do:

as.vector(do.call(rbind, vs))

vQ

Thanks, works fine.

Armin