kronecker {base}

R Documentation

Kronecker products on arrays

Description

Computes the generalised kronecker product of two arrays, X and Y. kronecker(X, Y) returns an array A with dimensions dim(X) * dim(Y).

Usage

kronecker(X, Y, FUN = "*", make.dimnames = FALSE, ...)
X %x% Y

Arguments

X	A vector or array.
Y	A vector or array.
FUN	a function; it may be a quoted string.
make.dimnames	Provide dimnames that are the product of the dimnames of X and Y.
...	optional arguments to be passed to FUN.

Details

If X and Y do not have the same number of dimensions, the smaller array is padded with dimensions of size one. The returned array comprises submatrices constructed by taking X one term at a time and expanding that term as FUN(x, Y, ...).

%x% is an alias for kronecker (where FUN is hardwired to "*").

Author(s)

Jonathan Rougier, J.C.Rougier@durham.ac.uk

References

Shayle R. Searle (1982) Matrix Algebra Useful for Statistics. John Wiley and Sons.

See Also

outer, on which kronecker is built and %*% for usual matrix multiplication.

Examples

# simple scalar multiplication
( M <- matrix(1:6, ncol=2) )
kronecker(4, M)
# Block diagonal matrix:
kronecker(diag(1, 3), M)

# ask for dimnames

fred <- matrix(1:12, 3, 4, dimnames=list(LETTERS[1:3], LETTERS[4:7]))
bill <- c("happy" = 100, "sad" = 1000)
kronecker(fred, bill, make.dimnames = TRUE)

bill <- outer(bill, c("cat"=3, "dog"=4))
kronecker(fred, bill, make.dimnames = TRUE)

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