# extract.array

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##### Extract a subset of an array, matrix or a vector with unknown dimensions

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.

Keywords
methods, programming
##### 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.

slice.index()

##### Aliases
• extract.array
• extract.array
• extract.matrix
• extract.default
##### 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))
Documentation reproduced from package R.utils, version 1.3.3, License: LGPL (>= 2.1)

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