About this;
> m <- matrix( 1:9, nr = 3 )
> dimnames( m ) <- list( c("d", "e", "f"), c("a", "b", "c") )
> data.frame( row = rep( rownames(m), ncol(m)), col = rep(
colnames(m), each = nrow(m)), data = as.vector(m) )
row col data
1 d a 1
2 e a 2
3 f a 3
4 d b 4
5 e b 5
6 f b 6
7 d c 7
8 e c 8
9 f c 9
or
data.frame( do.call( expand.grid, dimnames(m) ), data = as.vector(m))
Some timings on my machine with a 700x700 matrix:
> m <- matrix( rnorm( 700*700 ), nr = 700 )
> dimnames( m ) <- rep( list( as.character( 1:700) ), 2 )
> system.time( data.frame( row = rep( rownames(m), ncol(m)), col = rep(
colnames(m), each = nrow(m)), data = as.vector(m) ) )
user system elapsed
0.468 0.101 0.594
> system.time( data.frame( do.call( expand.grid, dimnames(m) ), data =
as.vector(m)) )
user system elapsed
0.432 0.106 0.551
Romain
Ian Coe wrote:
Hi,
Is there a way to convert a matrix into a vector representing all
permutations of values and column/row headings with native R functions?
I did this with 2 nested for loops and it took about 25 minutes to run
on a ~700x700 matrix. I'm assuming there must be a smarter way to do
this with R's vector commands, but being new to R, I'm having trouble
making it work.
Thanks,
Ian
[a] [b] [c]
[d] 1 4 7
[e] 2 5 8
[f] 3 6 9
a d 1
a e 2
a f 3
b d 4
b e 5
b f 6
c d 7
c e 8
c f 9
Ian Coe
Connective Capital Management, LLC
385 Homer Ave.
Palo Alto, CA 94301
(650) 321-4826 ext. 03
CONFIDENTIALITY NOTICE: This e-mail communication (inclu...{{dropped:23}}
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--
Romain Francois
Independent R Consultant
+33(0) 6 28 91 30 30
http://romainfrancois.blog.free.fr
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