R: Extract or modify diagonals of a matrix

sdiag {mgcv} | R Documentation

## Extract or modify diagonals of a matrix

### Description

Extracts or modifies sub- or super- diagonals of a matrix.

### Usage

    sdiag(A,k=0)
    sdiag(A,k=0) <- value

### Arguments

`A` | a matrix
`k` | sub- (negative) or super- (positive) diagonal of a matrix. 0 is the leading diagonal.
`value` | single value, or vector of the same length as the diagonal.

### Value

A vector containing the requested diagonal, or a matrix with the requested diagonal replaced by `value`.

### Author(s)

Simon N. Wood simon.wood@r-project.org

### Examples

    require(mgcv)
    A <- matrix(1:35,7,5)
    A
    sdiag(A,1) ## first super diagonal
    sdiag(A,-1) ## first sub diagonal

    sdiag(A) <- 1 ## leading diagonal set to 1
    sdiag(A,3) <- c(-1,-2) ## set 3rd super diagonal

[Package mgcv version 1.8-17 Index]