Laura Bonnett wrote:
crosstable[,,expand[d,1],expand[d,2],expand[d,3],...expand[d,n]]
crosstable is just a crosstabulation of an n+2-dimensional dataset and
I am trying to pick out those that are in combination 'd' of expand.
So for example, for 5-dimensional data using your example:
Var1 Var2 Var3
1 1 1 1
2 2 1 1
3 3 1 1
4 1 2 1
5 2 2 1
6 3 2 1
7 1 1 2
8 2 1 2
9 3 1 2
10 1 2 2
11 2 2 2
12 3 2 2
d refers to the row of the matrix above - d=2 is 2,1,1 so
crosstable[,,2,1,1] would retrieve all the data where Var1 =2, Var2=1,
Var3=1 and the two remaining variables are given in the
crosstabulations for all values.
Is that any better?
OK I think I understand. The magic package uses this type of
construction extensively, but not this particular one.
It's trickier than I'd have expected.
Try this:
f <- function(a,v){
jj <-
sapply(dim(a)[seq_len(length(dim(a))-length(v))],seq_len,simplify=FALSE)
jj <- c(jj , as.list(v))
do.call("[" , c(list(a) , jj, drop=TRUE))
}
[you will have to coerce the output from expand.grid() to a matrix in
order to extract a row from it]
HTH
rksh
--
Robin K. S. Hankin
Senior Research Associate
Cambridge Centre for Climate Change Mitigation Research (4CMR)
Department of Land Economy
University of Cambridge
[EMAIL PROTECTED]
01223-764877
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