colcomp

Scilab Function
Last update : 25/04/2007

colcomp - column compression, kernel, nullspace

### Calling Sequence

  `[W,rk]=colcomp(A [,flag] [,tol])`

### Parameters

- `A` : real or complex matrix
- `flag` : character string
- `tol` : real number
- `W` : square non-singular matrix (change of basis)
- `rk` : integer (rank of `A` )

### Description

Column compression of `A` : `Ac = A*W` is column compressed i.e

`Ac=[0,Af]` with `Af` full column rank, rank(`Af` ) = rank(`A` ) = `rk` .

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

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

The `ma-rk` first columns of `W` span the kernel of `A` when `size(A)=(na,ma)`

### Examples

    A=rand(5,2)*rand(2,5);
    [X,r]=colcomp(A);
    norm(A*X(:,1:$-r),1)

### See Also

`rowcomp` , `fullrf` , `fullrfk` , `kernel` ,

### Author

F.D.;