rcm: Use the RCM algorithm to permute to banded matrix

In lotri: A Simple Way to Specify Symmetric, Block Diagonal Matrices

Use the RCM algorithm to permute to banded matrix

Description

The RCM stands for the reverse Cuthill McKee (RCM) algorithm which is used to permute the matrix to a banded matrix.

Usage

rcm(x)

Arguments

x	A symmetric matrix

Value

A permuted matrix that should be banded

Examples

m <- lotri({
 a + b + c + d + e + f + g + h + i + j + k + l + m + n + o +
 p ~ c(0.4, 0, 0.3, 0, 0, 0, -0.1, 0, 0, 0.2, 0, 0, 0,
       0, 0.5, 0, 0, 0, 0, 0, 1.3, 0, 0, 0, 0, 0, -0.6, 0.8,
       0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0.2,
       0, 0, 0, 0, 0, 0, 0, 0, 0, 0.9, 0, 0, 0, 0, 0, 0, 0,
       0, 0, 0, 0.9, 0, 0, 0, 0, 0, 0, 0, 0, 0, -0.2, 0, 0.3,
       0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2.1, 0.2, 0, 0, 0.2,
       0, 0, 0, 0, 0, 0, 0, 0, 0, 0.4, 0, 0, 0, 0, 0, -1.1,
       0.9, 0, 0, 0, 0, 0, 0, 0, 4.7, 0, 0, 0, 0, 0, 0, 0, 0,
       0, 0.5, 0, 0.2, 0, 0, 0, 1.9)
})

rcm(m)

lotri documentation built on Aug. 8, 2025, 6:12 p.m.