calculus (version 0.3.2)

diagonal: Tensor Diagonals

Description

Functions to extract or replace the diagonals of an array, or construct a diagonal array.

Usage

diagonal(x = 1, dim = rep(2, 2))
diagonal(x) <- value

Arguments

x

an array from which to extract the diagonals, or a vector giving the diagonal values to construct the array.

dim

the dimensions of the (square) array to construct when x is a vector.

value

vector giving the values of the diagonal entries.

Value

Vector of the diagonal entries of x if x is an array. If x is a vector, returns the diagonal array with the entries given by x.

Functions

• diagonal<-: set diagonals.

References

Guidotti, E. (2020). "calculus: High dimensional numerical and symbolic calculus in R". https://arxiv.org/abs/2101.00086

See Also

Other tensor algebra: contraction(), delta(), einstein(), epsilon(), index()

Examples

# NOT RUN {
### 3x3 matrix
diagonal(x = 1, dim = c(3,3))

### 2x2x2 array
diagonal(x = 1:2, dim = c(2,2,2))

### extract diagonals 
x <- diagonal(1:5, dim = c(5,5,5))
diagonal(x)

### set diagonals
x <- array(0, dim = c(2,2,2))
diagonal(x) <- 1:2
x

# }