Eigenvalue Accuracy in Matlab

"Peter K." <p.kootsookos@remove.ieee.org> wrote in message
news:uek4hgp00.fsf@remove.ieee.org...
> "Mr Hrundi V Bakshi" <mrhrundivbakshi@hotmail.com> writes:
>
> > "Peter K." <p.kootsookos@remove.ieee.org> wrote in message
> > news:uhd9ejyc8.fsf@remove.ieee.org...
> > > "Mr Hrundi V Bakshi" <mrhrundivbakshi@hotmail.com> writes:
> > >
> > > > Good point. Also, a dconig for the A in question reveals that
Matlab is
> > not
> > > > to be trusted in fp arithmetic: indeed that Tr(A) == 0 is
sufficient to
> > > > ..., anyways, do your own homework!
> > >
> > > You're just upset because you gave the wrong advice, and don't
realise
> > > that "0.0000" in matlab is not really zero.  Go do your own homework!
> > >
> >
> > I couldn't give a rat's ass what Matlab produces: it's an overpriced
tool
> > within the budget of the naive.
> > For the A in question, its eigenvalues are threefold degenerately
naught 0,
> > not "0.0000" or any othersuch boloney. Sorry that this escaped you.
>
> It escaped you, that's all I was pointing out. :-)
>

Agreed. Now, if only Matlab could figure this!

--
Ciao,

Hrundi V.B.

Eric Jacobsen wrote:
> On Tue, 13 Dec 2005 09:34:36 -0800, "Bhaskar Thiagarajan"
> <bhaskart@deja.com> wrote:
> 
> 
>>"Cleve Moler" <moler@mathworks.com> wrote in message
> 
> 
> ...
> 
> 
>>>This particular example happens to be both singular and defective.  If
>>>any scalar value is added to the diagonal elements, then the matrix is no
>>>longer singular, but that scalar value becomes the sensitive eigenvalue.
>>>
>>>  -- Cleve
>>>  moler@mathworks.com
>>
>>Wow! Cleve Moler writing on comp.dsp - I know we do a fair amount of
>>Mathworks bashing here, but I'm impressed.
>>For those who don't know, he was one of the founders.
>>
>>Cheers
>>Bhaskar
> 
> 
> He's been here plenty of times in the past, including during our
> Matlab bashing regarding ones-based indexing.   His technical input is
> always good and welcomed (as cited above), but he's seemed completely
> unsympathetic regarding the indexing issues.

Not just that but they used to be a lot free'r with tee shirts and nerf 
Frisbees.  There were also some undocumented function in versions prior 
to 4, like "lala" that appeared to be censored by the thought police. 
They don't include the Lena image in their gallery, either.  They just 
seems to have lost all the fun aspects of the old days.


> 
> There are a number of well-known folks, techno-deities, so to speak,
> that show up here from time to time.  It's always nice to hear from
> them, IMHO.
> 
> Eric Jacobsen
> Minister of Algorithms, Intel Corp.
> My opinions may not be Intel's opinions.
> http://www.ericjacobsen.org

On Wed, 14 Dec 2005 08:27:51 -0500, Stan Pawlukiewicz
<spam@spam.mitre.org> wrote:

>Not just that but they used to be a lot free'r with tee shirts and nerf 
>Frisbees.

Wow, you have a good memory.   I'd forgotten about the shirts and
Frisbees.   Those were the days...  ;)

Oh, wait, I'm just realizing that I've been wearing that shirt for a
long time.  It's now only worn in the garage and has some holes in
it...probably close to becoming a shop rag...

>  There were also some undocumented function in versions prior 
>to 4, like "lala" that appeared to be censored by the thought police. 
>They don't include the Lena image in their gallery, either.  They just 
>seems to have lost all the fun aspects of the old days.

Yeah, bummer.  :(

Eric Jacobsen
Minister of Algorithms, Intel Corp.
My opinions may not be Intel's opinions.
http://www.ericjacobsen.org

Eric Jacobsen <eric.jacobsen@ieee.org> writes:

> 
> >  There were also some undocumented function in versions prior 
> >to 4, like "lala" that appeared to be censored by the thought police. 
> >They don't include the Lena image in their gallery, either.  They just 
> >seems to have lost all the fun aspects of the old days.
> 
> Yeah, bummer.  :(
> 

Yeah, I remember typing one expletive into matlab, in frustration, and
it came back with "Your place or mine?".

Most amusing. :0)

Ciao,

Peter K.