[R] exclude a vector value from another vector

Greg Snow Greg.Snow at imail.org
Tue Dec 2 17:03:41 CET 2008

Others have shown ways to remove your sample from the population, but this may be doing things the long way.  If you just want several samples from the same population without overlap between any of the samples, just take one sample of size equal to the sum of the individual sample sizes, randomize the order, then split it into the individual samples.

For example, to get 6 samples of size 4 from the population of "LETTERS":

> mysamples <- matrix( sample(LETTERS, 24), ncol=6 )
> mysamples
     [,1] [,2] [,3] [,4] [,5] [,6]
[1,] "F"  "L"  "H"  "A"  "S"  "P"
[2,] "M"  "D"  "U"  "N"  "G"  "C"
[3,] "O"  "R"  "E"  "V"  "K"  "W"
[4,] "J"  "X"  "B"  "T"  "Z"  "I"

Now each column is a sample, us apply or a for loop to work on each one.

Hope this helps,

Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
greg.snow at imail.org

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of Hamid Hamid
> Sent: Monday, December 01, 2008 12:17 PM
> To: r-help at r-project.org
> Subject: [R] exclude a vector value from another vector
> Dear All,
> I am trying to build a program which will take repeated samples (w/o
> replacement) from a population of values. The interesting catch is that
> I
> would like the sample values to be removed from the population, after
> each
> sample is taken.
> For example:
> pop<-c(1,5,14,7,9,12,18,19,65,54)
> sample(pop, 2) = lets say, (5,54)
> ## This is where I would like values (5, 54) to be removed from the
> population vector, giving a new "current" population vector:
> "new" pop = [1,14,7,9,12,18,19,65]
> and has length 8 instead of 10.
> In the cases when the size of pop and deriven sample of it is enough
> large
> using the following command is not helpful.
> newpop<-pop[-c(2,10)]
> One could simplify my question in this way: how we can exclude a sub
> vector
> values from a super  vector value (i.e sub vecor values are subset of
> super
> vector values).
> Thanks in advance.
> Hamid
>         [[alternative HTML version deleted]]
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