[R] all combinations of the elements of two vectors

[Campbell, Desmond]

Petr, Jorge, Daniel,

Yes you could also use outer() instead of expand.grid(). 
This is quite useful to know.

Also I didn't know you could turn a matrix into a vector by setting its dimensions to NULL like that. I always used as.vector( m ).
And (as I've just discovered) you can use it to reconfigure the matrix's shape to any that contains the same number of elements.

Thanks very much one and all.

Regards
Desmond


-----Original Message-----
From: Petr PIKAL [mailto:petr.pikal at precheza.cz] 
Sent: 29 August 2011 07:24
To: Campbell, Desmond
Cc: r-help at R-project.org
Subject: Odp: [R] all combinations of the elements of two vectors

Hi
> 
> Dear R-help readers,
> 
> I'm sure this problem has been answered but I can't find the solution.
> 
> I have two vectors
> v1 <- c("a","b")
> v2 <- c(1,2,3)
> I want an easy way to produce every possible combination of v1, v2 
elements
> Ie I want to produce
> c("a1","a2","a3", "b1","b2","b3")

Another option is

z<-outer(x,y, paste, sep="")
dim(z)<-NULL
> z
[1] "a1" "b1" "c1" "a2" "b2" "c2" "a3" "b3" "c3"

which gives the result in different order

or

z<-as.vector(t(z))
> z
[1] "a1" "a2" "a3" "b1" "b2" "b3" "c1" "c2" "c3"

Which gives you desired order.

Regards
Petr

> 
> regards
> Desmond
> 
> Desmond Campbell
> Dept of Biostatistics and Computing, Institute of Psychiatry (KCL),
> PO Box 20, De Crespigny Park, Denmark Hill London, SE5 8AF
> 
> Tel 020 7848 0309
> Email D.Campbell at iop.kcl.ac.uk<mailto:D.Campbell at iop.kcl.ac.uk>
> 
> 
> 
>    [[alternative HTML version deleted]]
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