R.utils (version 1.5.8)

extract.array: Extract a subset of an array, matrix or a vector with unknown dimensions

Description

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.

Usage

## S3 method for class 'array':
extract(x, ..., drop=FALSE, indices=list(...))

Arguments

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 v

drop

If TRUE, dimensions of length one are dropped, otherwise not.

Value

• Returns an array.

See Also

slice.index()

Examples

cat("Create an array 'x' with a random number of dimensions:
")
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("Array 'x':
")
print(x)


cat("Extract 'x[2:3,...]':
")
print(extract(x, "1"=2:3))

cat("Extract 'x[3,2:3,...]':
")
print(extract(x, "1"=3,"2"=2:3))

cat("Extract 'x[...,2:3]':
")
indices <- list(2:3)
names(indices) <- length(dim(x))
print(extract(x, indices=indices))