inconsistent condition numbers from cond, det, inv functions

[Rolf Fabian]

Ben Abbott wrote:
> 
> On Feb 7, 2008, at 7:00 AM, Rolf Fabian wrote:
> 
>> Ben, what' s the result for 1./cond(y) ?
>> Does Matlabs cond() have a similar argument 'p' too?
> 
> Yes!
> 
> Ben
> 

Thanks Ben. From your results I conclude that MatLab
is actually doing something very similar than I did for my
condh-function. I personally have good reasons not to
send any code any more to any Octave list. So, if you like,
make jwe happy by sending him a patched version of 'cond.m'
implementing a 2nd argument p which defines the mode of
(both) calls to 'norm.m'. In order to conform to ML, the default
mode should be p=2 as long as input matrix is regular (non-singular).

I've no idea why the ML-result for the 1st (singular) testmatrix x
from cond() differs from the 2-norm algorithm. This needs further
test with ML using singular input to cond(), but ML is not available
for me.

Rolf Fabian


-----
Rolf Fabian
<r dot fabian at jacobs-university dot de>

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