red¶

Purpose:

Reduce the size of a square matrix by omitting rows and columns.

Syntax:

B = red(A, b)
[B, b] = red(A, b)

Description:

B = red(A, b) reduces the square matrix A to a smaller matrix B by omitting rows and columns of A. The indices for rows and columns to be omitted are specified by the column vector b.

Example:

Assume that the matrix A is defined as

A\(= \begin{bmatrix} 1 & 2 & 3 & 4 \\ 5 & 6 & 7 & 8 \\ 9 & 10 & 11 & 12 \\ 13 & 14 & 15 & 16 \end{bmatrix}\)

and b as

b\(= \begin{bmatrix} 2 \\ 4 \end{bmatrix}\)

The statement B = red(A, b) results in the matrix

B\(= \begin{bmatrix} 1 & 3 \\ 9 & 11 \end{bmatrix}\)