| extract.array {R.utils} | R Documentation |
Extract a subset of an array, matrix or a vector with unknown dimensions.
This method is useful when you do not know the number of dimensions of the object your wish to extract values from, cf. example.
## S3 method for class 'array': extract(x, ..., drop=FALSE, indices=list(...))
x |
An array or a matrix. |
... |
These arguments are by default put into the
indices list. |
indices |
A list of index vectors to be extracted.
The names (coerced to integers) of the list elements are the
dimension indices for each of the index vectors. |
drop |
If TRUE, dimensions of length one are dropped,
otherwise not. |
Returns an array.
Henrik Bengtsson (http://www.braju.com/R/)
cat("\nCreate an array 'x' with a random number of dimensions:\n")
maxdim <- 4
dim <- sample(3:maxdim, size=sample(2:maxdim, size=1), replace=TRUE)
ndim <- length(dim)
dimnames <- list()
for (kk in 1:ndim)
dimnames[[kk]] <- sprintf("%s%d", letters[kk], 1:dim[kk])
x <- 1:prod(dim)
x <- array(x, dim=dim, dimnames=dimnames)
cat("\nArray 'x':\n")
print(x)
cat("\nExtract 'x[2:3,...]':\n")
print(extract(x, "1"=2:3))
cat("\nExtract 'x[3,2:3,...]':\n")
print(extract(x, "1"=3,"2"=2:3))
cat("\nExtract 'x[...,2:3]':\n")
indices <- list(2:3)
names(indices) <- length(dim(x))
print(extract(x, indices=indices))