R help - May 2004 - anyone know how to combine two vector with some # overlaped?

Hi, there,

Suppose I have two vector say x=c(1 2 3 4 5) and y=(2
3 6 7). Then I want to combine these two vector
together and get z=c(1 2 3 4 5 6 7) with 2 and 3 only
appear once. I want to extend this one to a general
case(say more than 100 elements in x and y and each
time I don't know which elements are the same). Do you
happen to know how to do this and which command should
use?

Thank you very much. Please reply to this email. Any
kind help would be greatly appreciated.

Mike

Try

x <- c(1,2,3,4,5)
y <- c(2,3,6,7)
z <- c(x,y)[!duplicated(c(x,y))] 

HTH,
Jules

Mike wrote:
> 
> Hi, there,
> 
> Suppose I have two vector say x=c(1 2 3 4 5) and y=(2
> 3 6 7). Then I want to combine these two vector
> together and get z=c(1 2 3 4 5 6 7) with 2 and 3 only
> appear once. I want to extend this one to a general
> case(say more than 100 elements in x and y and each
> time I don't know which elements are the same). Do you
> happen to know how to do this and which command should
> use?
> 
> Thank you very much. Please reply to this email. Any
> kind help would be greatly appreciated.
> 
> Mike
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://www.stat.math.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html
-- 
---
Julian Taylor			phone: +61 8 8303 6751
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Glen Osmond SA 5064

"There is no spoon."   -- Orphan boy  
---

Mike wrote:
> Hi, there,
> 
> Suppose I have two vector say x=c(1 2 3 4 5) and y=(2
> 3 6 7). Then I want to combine these two vector
> together and get z=c(1 2 3 4 5 6 7) with 2 and 3 only
> appear once. I want to extend this one to a general
> case(say more than 100 elements in x and y and each
> time I don't know which elements are the same). Do you
> happen to know how to do this and which command should
> use?
> 
> Thank you very much. Please reply to this email. Any
> kind help would be greatly appreciated.
> 
> Mike
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://www.stat.math.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html
See ?unique

Uwe Ligges

Mike wrote:
>Hi, there,
>
>Suppose I have two vector say x=c(1 2 3 4 5) and y=(2
>3 6 7). Then I want to combine these two vector
>together and get z=c(1 2 3 4 5 6 7) with 2 and 3 only
>appear once.
>
union(x,y)

R provides several set operators. See ?union.

Christophe Pallier

If you want this:

	> Suppose I have two vector say x=c(1 2 3 4 5) and y=(2
	> 3 6 7). Then I want to combine these two vector
	> together and get z=c(1 2 3 4 5 6 7) with 2 and 3 only
	> appear once.

Julian Taylor <julian.taylor at adelaide.edu.au> suggests:
	x <- c(1,2,3,4,5)
	y <- c(2,3,6,7)
	z <- c(x,y)[!duplicated(c(x,y))] 
	
But you can do it in one step:
	z <- unique(c(x,y))

I don't know how unique() is implemented, but using a hash table it
_could_ be done in linear expected time, and in practice it seems to
be pretty quick, more than quick enough for a few hundred elements.