Re: fitting functions which contain 'i'

[Jaroslav Hajek]

On Thu, Feb 5, 2009 at 6:19 PM, Harbinson, Jeremy
<address@hidden> wrote:
> Hi,
> Does Octave have any ability to fit a function which contains 'i' (the
> square root of -1 in case 'i' is as unclear on your screen as it is on
> mine). The least squares fitting tool does not seem to work, or at least I
> could not get to work, and these are two quite different things, of course.
>

A least squares problem with complex equations but real variables can
easily be turned into a real one by decomposing the real and complex
part. The same, of course holds for a complex/complex problem, but it
is sub-optimal if the equations posess a complex derivative, in which
case it's better to work with complex jacobian directly.
I think the new Octave's fsolve (to be available in 3.2) should work
with complex numbers, too, though I haven't yet tested.

> I need something that can be used to fit bioimpedance data and to date I
> have been using the LEVM programme, and though this works very well for me
> it is somewhat user unfriendly and certainly for our students 'somewhat user
> unfriendly' means, in most cases, total collapse.
>
> all the best,
> Jeremy Harbinson
>

Perhaps if you describe the problem more closely, you may get more
detailed help.

cheers


-- 
RNDr. Jaroslav Hajek
computing expert
Aeronautical Research and Test Institute (VZLU)
Prague, Czech Republic
url: www.highegg.matfyz.cz