diag: Polynomial matrix Diagonals Extract or construct a diagonal polynomial matrix.

Description

Polynomial matrix Diagonals Extract or construct a diagonal polynomial matrix.

Usage

diag(x = 1, nrow, ncol, names = TRUE)
# S4 method for polynomial
diag(x, nrow, ncol)
# S4 method for polyMatrix
diag(x)

Arguments

a polynomial matrix, or a polynomial, or an R object

nrow, ncol

optional dimensions for the result when x is not a matrix

names

not used for polynomial matrices

Methods (by class)

polynomial: for a polynomial, returns a polynomial matrix with the given diagonal
polyMatrix: for a polynomial matrix extracts diagonal

For polynomial matrix, neither nrow nor ncol cannot be provided.

Details

In case of polynomial objects, diag has 2 distinct usage:

x is a polynomial, returns a polynomial matrix the given diagonal and zero off-diagonal entries.
x is a polynomial matrix, returns a vector as a polynomial matrix of diagonal elements

For polynomial, either nrow or ncol must be provided.

Examples

Run this code

# NOT RUN {
# numericals and numerical matrices
diag(matrix(1:12, 3, 4)) ## 1 5 8
diag(9, 2, 2)
##      [,1] [,2]
## [1,]    9    0
## [2,]    0    9



# polynomial
diag(parse.polynomial("1+x+3x^2"), 2, 3)
##                [,1]           [,2]   [,3]
## [1,]   1 + x + 3x^2              0      0
## [2,]              0   1 + x + 3x^2      0


# polynomial matrix
diag(parse.polyMatrix(
  "-3 + x^2, 2 + 4 x,  -x^2",
  "       1,       2, 3 + x",
  "      2x,       0, 2 - 3x"
))
##            [,1]   [,2]     [,3]
## [1,]   -3 + x^2      2   2 - 3x

# }