R help - Nov 2003 - sampling without repetition

Hi,
  I'm trying to write a function that will divide a given range of
numbers into 3 sets using sample(), without repetition. Currently I'm
trying this approach:

r <- 1:10
s1 <- sample(r,size=3)

Next, I want to remove the selected elements from r and sample() from
the remainder.

r <- r[ -(r=s1) ]
s2 <- sample(r,size=3)

When I go to remove the elements contained in s2 from r I get an error:

r <- r[ -(r=s2) ]
Error: subscript out of bounds

I'm not sure why this is happening. I tried replacing the '=' with
'=='
but I get another error 

Warning message:
longer object length
        is not a multiple of shorter object length in: r == s1

Essentially what I need is to get the indices into r of the elements of
s1 & s2. I have looked at which but I cant seem to work out how I can
get the indices into r of all the elements of, say, s1.

Does anybody have any suggestions? (Of course if there is a more elegant
way of doing this whole thing I would appreciate any pointers)

Thanks,

-------------------------------------------------------------------
Rajarshi Guha <rxg218 at psu.edu> <http://jijo.cjb.net>
GPG Fingerprint: 0CCA 8EE2 2EEB 25E2 AB04 06F7 1BB9 E634 9B87 56EE
-------------------------------------------------------------------
A committee is a life form with six or more legs and no brain.
-- Lazarus Long, "Time Enough For Love"

Rajarshi  -

Do you want three sets, three disjoint sets, or sets of
size three ?  It's not clear what you are attempting to do.

-  tom blackwell  -  u michigan medical school  -  ann arbor  -

On Mon, 17 Nov 2003, Rajarshi Guha wrote:
> Hi,
>   I'm trying to write a function that will divide a given range of
> numbers into 3 sets using sample(), without repetition. Currently I'm
> trying this approach:
>
> r <- 1:10
> s1 <- sample(r,size=3)
>
> Next, I want to remove the selected elements from r and sample() from
> the remainder.
>
> r <- r[ -(r=s1) ]
> s2 <- sample(r,size=3)
>
> When I go to remove the elements contained in s2 from r I get an error:
>
> r <- r[ -(r=s2) ]
> Error: subscript out of bounds
>
> I'm not sure why this is happening. I tried replacing the '='
with '=='
> but I get another error
>
> Warning message:
> longer object length
>         is not a multiple of shorter object length in: r == s1
>
> Essentially what I need is to get the indices into r of the elements of
> s1 & s2. I have looked at which but I cant seem to work out how I can
> get the indices into r of all the elements of, say, s1.
>
> Does anybody have any suggestions? (Of course if there is a more elegant
> way of doing this whole thing I would appreciate any pointers)
>
> Thanks,
>
> -------------------------------------------------------------------
> Rajarshi Guha <rxg218 at psu.edu> <http://jijo.cjb.net>
> GPG Fingerprint: 0CCA 8EE2 2EEB 25E2 AB04 06F7 1BB9 E634 9B87 56EE
> -------------------------------------------------------------------

> r <- 1:30
 > # Random allocation to sets
 > tapply(r, sample(1:3,length(r),rep=T), c)
$"1"
  [1]  1  3  8 12 15 16 18 20 21 25 29

$"2"
  [1]  2  5  6  7  9 10 13 14 17 19 22 27 30

$"3"
[1]  4 11 23 24 26 28

 > # Equal size sets (approximately)
 > tapply(r, sample(seq(length(r))%%3), c)
$"0"
  [1]  1  6  9 10 12 15 22 24 28 30

$"1"
  [1]  2  3  4  5  8 17 18 21 23 27

$"2"
  [1]  7 11 13 14 16 19 20 25 26 29

 >

At Monday 07:28 PM 11/17/2003 -0500, you wrote:
>Hi,
>   I'm trying to write a function that will divide a given range of
>numbers into 3 sets using sample(), without repetition. Currently I'm
>trying this approach:
>
>r <- 1:10
>s1 <- sample(r,size=3)
>
>Next, I want to remove the selected elements from r and sample() from
>the remainder.
>
>r <- r[ -(r=s1) ]
>s2 <- sample(r,size=3)
>
>When I go to remove the elements contained in s2 from r I get an error:
>
>r <- r[ -(r=s2) ]
>Error: subscript out of bounds
>
>I'm not sure why this is happening. I tried replacing the '='
with '=='
>but I get another error
>
>Warning message:
>longer object length
>         is not a multiple of shorter object length in: r == s1
>
>Essentially what I need is to get the indices into r of the elements of
>s1 & s2. I have looked at which but I cant seem to work out how I can
>get the indices into r of all the elements of, say, s1.
>
>Does anybody have any suggestions? (Of course if there is a more elegant
>way of doing this whole thing I would appreciate any pointers)
>
>Thanks,
>
>-------------------------------------------------------------------
>Rajarshi Guha <rxg218 at psu.edu> <http://jijo.cjb.net>
>GPG Fingerprint: 0CCA 8EE2 2EEB 25E2 AB04 06F7 1BB9 E634 9B87 56EE
>-------------------------------------------------------------------
>A committee is a life form with six or more legs and no brain.
>-- Lazarus Long, "Time Enough For Love"
>
>______________________________________________
>R-help at stat.math.ethz.ch mailing list
>https://www.stat.math.ethz.ch/mailman/listinfo/r-help
Tony Plate   tplate at acm.org