Re: What to give as "real column vector of initial parameters" to nonlin_curvefit?

[Kai Torben Ohlhus]

On 6/12/20 2:20 AM, Doron Behar wrote:> [...]
> Since I'm already here, perhaps you could help me a bit further:
>
> I set this parametric function:
>
>     harmonic_param_func = @(p, t) p(1) * exp(-t/(2 * p(2))) *
cos(p(3)*t + p(4))
>
> And I call nonlin_curvefit like this:
>
>     [p, fy, cvg, outp] = nonlin_curvefit( ...
>         harmonic_param_func, [ ...
>             guessed_max_amplitude; ...
>             guessed_tau; ...
>             guessed_period; ...
>             guessed_phase
>         ], ...
>         counts, times ...
>     );
>
> Where the variables guessed_* are corresponding values I think may be a
> good starting guess for the fitting algorithm. But I get this error when
> I call it as so:
>
>     error: NA: invalid class name
>     error: called from
>         __nonlin_residmin__ at line 212 column 21
>         nonlin_curvefit at line 83 column 22
>         ./harmonic-oscillator.m at line 50 column 21
>
> And if I use `,` instead of `;` I get the error:
>
>     error: initial parameters must be either a structure or a column
vector
>     error: called from
>         __nonlin_residmin__ at line 101 column 7
>         nonlin_curvefit at line 83 column 22
>         ./harmonic-oscillator.m at line 50 column 21
>
> Maybe I'm just not fluent yet in octave's / matlab's data types. But,
> the 2nd error intrigued me more: Is it possible to use a struct where my
> `p` is, in the fitting function? If so that's sound like another
> undocumented detail of the function?
>
> Doron.

You function call does not look that wrong, but the devil is in the
detail.  Can you sent us a minimal working example containing all
"guessed_*" values and "counts", "times"?

Kai