Re: Additional methods for QRdecomposition class

[Cleve Moler <moler@mathworks.com>]

On Thu, 13 Aug 1998, Douglas Bates wrote:

> May I suggest that more methods be added to the QRdecomposition class?
> In particular, I would suggest
>  public Matrix QMultiply (Matrix B)
> that forms QB from B and
>  public Matrix QTransMultiply (Matrix B)
> that forms transpose(Q)B from B.
> 
> It may even be worthwhile having methods such as
>  public Matrix QMultiplyEquals (Matrix B)
> and
>  public Matrix QTransMultiplyEquals (Matrix B)
> to provide in-place versions of these operations.
> 
> Other possibilities are methods to project the columns of a Matrix B
> onto the column space of the original matrix X or onto its orthogonal
> complement.  These are very useful in statistical computing.  Back in
> the days of Linpack these operations were available through dqrsl.
> 
> 

Thanks, Doug.  I agree.  This was already on my list of possible
additions.  Except I think the names should be  QTimes and
QTransposeTimes, to be consistent with "times" and "transpose".

  -- Cleve Moler
  moler@mathworks.com