On Aug 29, 2011, at 9:15 AM, Campbell, Desmond wrote:
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.
You can do that but it requires that you understand the ordering of
matrices if you want to avoid scrambling your indices. Since you seem
new to that concept, you should work through several small examples to
make sure you understand the effects of dimensional coercion.
You should also look at the aperm function and the abind package.
--
David.
Thanks very much one and all.
Regards
Desmond
-----Original Message-----
From: Petr PIKAL [mailto:petr.pi...@precheza.cz]
Sent: 29 August 2011 07:24
To: Campbell, Desmond
Cc: r-help@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.campb...@iop.kcl.ac.uk<mailto:d.campb...@iop.kcl.ac.uk>
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West Hartford, CT
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