Re: Fitting Nonlinear Complex Data(How do you do this?)

Hi,I was wondering if you got any (private) responses to
your query.
Matlab documentation provides a 'curve fitting guide' where
it is written that:
"For fitting curves in a case involving complex data set,
the data set should be split into real and imaginary parts"
An example is given, but boy, is that doc badly written!
I couldn't figure out how to make it work when using the
'fit' function.
Incidentally, and forgive my rant, I think it's ridiculous
that Mathworks has its users bend over backwards to perform
the fitting of complex expressions, something that is
pretty common in many engineering fields.



"Nathan Orloff" <orloffREMOVETHIS@xxxxxxxx> wrote in message
<fsuiqq$r54$1@xxxxxxxxxxxxxxxxxx>...
Hi all,

I saw the help on how to fit nonlinear parameters I did not
really find it too helpful. My goal is to use 'fit' to fit
some complex data I have. The function I am fitting is:

y(x) = a+(b-a)./(1+(sqrt(-1).*c.*(x)).^d

I tried doing the fit separately(real, then imaginary). The
issue is that it would be much better if I could fit both
parts simultaneously. Does anyone have any suggestions?

I was thinking you could concatenate the real and imaginary
parts into a single vector. And then make the cost functions
something like:

y' = real(y);
y'(1+length(y):2*length(y))=imag(y);

But although fit allows custom functions I don't see how to
do this inline.

Nate

.

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