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[Octave-bug-tracker] [bug #34953] Bug with qrdelete

From: Aswin Kannan
Subject: [Octave-bug-tracker] [bug #34953] Bug with qrdelete
Date: Wed, 30 Nov 2011 16:57:20 +0000
User-agent: Mozilla/5.0 (X11; Linux i686) AppleWebKit/534.30 (KHTML, like Gecko) Ubuntu/10.10 Chromium/12.0.742.112 Chrome/12.0.742.112 Safari/534.30


                 Summary: Bug with qrdelete
                 Project: GNU Octave
            Submitted by: aswink
            Submitted on: Wed 30 Nov 2011 04:57:14 PM GMT
                Category: None
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: None
                  Status: None
             Assigned to: None
         Originator Name: Aswin Kannan
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 3.2.4
        Operating System: GNU/Linux



This pertains to a bug with respect to the function 'qrdelete'. 
The version of octave that I'm using is 3.2.4. The operating system that I use
is linux-ubuntu-10.10 (maverick). 

A sample code fragment is as follows:

A = randn(7,5); [Q,R] = qr(A);
[Q1,R1] = qrdelete(Q,R,7,'row');

The error that I get is as follows:  

** On entry to DQRDER parameter number  7 had an illegal value
error: exception encountered in Fortran subroutine dqrder_

I think that this is a bug, since I get the same error when I try to delete a
row from a 
factorization with m > n (m being the number of rows and n being the number of
columns -- Q is of dimension m x m and R is of dimension m x n). I did try on
both 32 and 64 bit versions
of linux and I get the same error.

Also there is an issue with the help file/ documentation with qrdelete:
Typing 'help qrdelete' gives me the following (partly shown below):

 -- Loadable Function: [Q1, R1] = qrdelete (Q, R, J, ORIENT)
     Given a QR factorization of a real or complex matrix A = Q*R,
     Q unitary and R upper trapezoidal, return the QR factorization of
     [A(:,1:j-1) A(:,j+1:n)], i.e., A with one column deleted (if
     ORIENT is "col"), or the QR factorization of
     [A(1:j-1,:);A(:,j+1:n)], i.e., A with one row deleted (if ORIENT
     is "row").


In the line before the last "[A(1:j-1,:);A(:,j+1:n)]" it should be 

I presume the error is due to something similar with j > n (Consider a matrix
A -- m x n -- the operation should be with m and not n). 


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