[R] A co-occurrence matrix
Adaikalavan RAMASAMY
ramasamya at gis.a-star.edu.sg
Tue Nov 11 13:40:55 CET 2003
You can try the following commands, which I have not tested extensively,
m <- data.frame( object=c(1,2,3,4,5), group=c(1,2,1,1,3) )
tab <- table(m)
out <- tab %*% t(tab)
The above is OK if every object belongs to one group only. But if it does not, say as in "m2 <- rbind(m, c(1,3))", the values above 1 can occur on the diagonal indicating the number of membership that object has.
-----Original Message-----
From: r-help-bounces at stat.math.ethz.ch on behalf of Alexey Shipunov
Sent: Tue 11/11/2003 18:49
To: R-help at stat.math.ethz.ch
Cc:
Subject: [R] A co-occurrence matrix
Dear R experts,
I have a matrix (from some sort of
classification) like this:
object group
[1,] 1 1
[2,] 2 2
[3,] 3 1
[4,] 4 1
[5,] 5 3
And I need something like this:
[,1] [,2] [,3] [,4] [,5]
[1,] 1 0 1 1 0
[2,] 0 1 0 0 0
[3,] 1 0 1 1 0
[4,] 1 0 1 1 0
[5,] 0 0 0 0 1
where all zeros mean that these objects are not
in same group, and vice versa.
Is there a relatively simple way to construct co-
uccurence matrices of type shown above?
Any help would be appreciated,
=================================
Dr. Alexey B. Shipunov
Section of Molecular Systematics
Jodrell Laboratory
Royal Botanic Gardens, Kew,
Richmond, Surrey, TW9 3DS, U.K.
e-mail: a.shipunov at rbgkew.org.uk
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