[12710] in Athena Bugs
decmips 7.7G: Matlab
daemon@ATHENA.MIT.EDU (dkwinkel@MIT.EDU)
Thu Oct 6 21:27:03 1994
From: dkwinkel@MIT.EDU
To: bugs@MIT.EDU
Date: Thu, 06 Oct 1994 21:26:55 EDT
System name: m37-312-13
Type and version: KN01 7.7G
Display type: PMAX-MFB
What were you trying to do?
QR decomposition to find leastsquares solution to Ax=b
Rx=Q'b backwards solve
What's wrong:
Function qr and backwards solving gives a different result than
A'Ax=A'b and subsequent LU decomposition and solving with slu and slv
functions
the result only differs in the first element of the x vector
the signs of the first row of the R matrix are different
from the ones I get with a code I wrote for Householder
What should have happened:
There should only be one least squares solution.
Please describe any relevant documentation references:
I could send you my diary file and my code
