Thanks for all the replies!Unfortunately the solutions only work for
extracting subsets of the data (which was exactly what I was asking for)
and not to replace subsets with other values. I used them, however, to
program a rather akward function to do that. Seems I found one of the
few aspects where Matlab actually is slightly easier to use than R.
Thanks for your help!
Jannis
On 08/01/2011 05:50 PM, Gene Leynes wrote:
What do you think about this?
apply(data, 3, '[', indices)
On Mon, Aug 1, 2011 at 4:38 AM, Jannis<bt_jan...@yahoo.de> wrote:
Dear R community,
I have a general question regarding indexing in multidiemensional arrays.
Imagine I have a three dimensional array and I only want to extract on
vector along a single dimension from it:
data<- array(rnorm(64),dim=c(4,4,4))
result<- data[1,1,]
If I want to extract more than one of these vectors, it would now really
help me to supply a logical matrix of the size of the first two dimensions:
indices<- matrix(FALSE,ncol=4,nrow=4)
indices[1,3]<- TRUE
indices[4,1]<- TRUE
result<- data[indices,]
This, however would give me an error. I am used to this kind of indexing
from Matlab and was wonderingt whether there exists an easy way to do this
in R without supplying complicated index matrices of all three dimensions or
logical vectors of the size of the whole matrix?
The only way I could imagine would be to:
result<- data[rep(as.vector(indices),**times=4)]
but this seems rather complicated and also depends on the order of the
dimensions I want to extract.
I do not want R to copy Matlabs behaviour, I am just wondering whether I
missed one concept of indexing in R?
Thanks a lot
Jannis
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