kernel kernel, null space

## Syntax

    W=kernel(A [,tol,[,flag])

## Arguments

A

  full real or complex matrix or real sparse matrix

flag

  character string `'svd'` (default) or `'qr'`

tol

  real number

W

  full column rank matrix

## Description

`W=kernel(A)` returns the kernel (null space) of `A`, and `size(W,2)` is the nullity of A. If A has full column rank then an empty matrix [] is returned.

`flag` and `tol` are optional parameters: `flag = 'qr'` or `'svd'` (default is `'svd'`).

`tol` = tolerance parameter (of order `%eps` as default value).

## Examples

    A=rand(3,1)*rand(1,3);
    A*kernel(A)
    A=sparse(A);
    clean(A*kernel(A))

## See also

- colcomp
- fullrf
- fullrfk
- linsolve