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
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
