R help - Sep 2008 - isolate elements in vector that match one of many possible values

Hi all,

I want to get the index numbers of all elements of a vector which match any
of a long series of possible values.  Say x <- c(1,2,3,4) and I want to know
which values are equal to 1, 2 or 4.  I could do

which(x == 1 | x==2 | x==4)
[1] 1 2 4

This gets really ugly though, when the list of values of interest is really
long.  Is there a nicer way to do this?  Something akin to the MySQL
construction in(), as in

#MySQL script example
Select * from table where parameter in(x,y,z);

Thanks!

-- 
W. Andrew Barr
Biological Anthropology
University of Texas at Austin

	[[alternative HTML version deleted]]

On 9/09/2008, at 1:55 PM, Andrew Barr wrote:
> Hi all,
>
> I want to get the index numbers of all elements of a vector which  
> match any
> of a long series of possible values.  Say x <- c(1,2,3,4) and I  
> want to know
> which values are equal to 1, 2 or 4.  I could do
>
> which(x == 1 | x==2 | x==4)
> [1] 1 2 4
>
> This gets really ugly though, when the list of values of interest  
> is really
> long.  Is there a nicer way to do this?
which(x%in%c(1,2,4))

	cheers,

		Rolf Turner

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Check out ?match, ?"%in%"
> x <- c(1,2,3,4)
> y <- c(1,2,4)
> match(y,x)
[1] 1 2 4
>
--Adam

On Mon, 8 Sep 2008, Andrew Barr wrote:
> Hi all,
> 
> I want to get the index numbers of all elements of a vector which match any
> of a long series of possible values.  Say x <- c(1,2,3,4) and I want to
know
> which values are equal to 1, 2 or 4.  I could do
> 
> which(x == 1 | x==2 | x==4)
> [1] 1 2 4
> 
> This gets really ugly though, when the list of values of interest is really
> long.  Is there a nicer way to do this?  Something akin to the MySQL
> construction in(), as in
> 
> #MySQL script example
> Select * from table where parameter in(x,y,z);
> 
> Thanks!
> 
> -- 
> W. Andrew Barr
> Biological Anthropology
> University of Texas at Austin
>
> 	[[alternative HTML version deleted]]
> 
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