Hi Peter,
On Wed, Jan 5, 2011 at 7:07 PM, Peter W. Draper <[log in to unmask]> wrote:
> On Mon, 3 Jan 2011, Matthijs H.D. van der Wiel wrote:
>
>> Additional question about the "deblend" script in starjava/bin/splat/
>> : is it possible to get more decimals on the parameter errors? For
>> example, I currently get this in the "report.log" output file:
>>
>> Post-fit: GaussianFitter[flux = 7.295523848504501, (+/- 0.0), scale =
>> 1.1952008680668813, (+/- 0.0), centre = -6.87900360112492, (+/- 0.0),
>> sigma = 2.435149604227493(+/- 0.0), FWHM = 5.734339100684084(+/- 0.0),
>> ]
>>
>> All I can infer from this is that the errors on each parameter are
>> smaller than 0.05 in the corresponding unit.
>
> Hi Matthijs,
>
> this probably indicates that your input spectrum does not have any variances
> and in that case the attempt to guess errors using a reduced chi-square of
> one isn't working (too good a fit, correlated data might do that).
That's true, my spectrum does not have a variance array associated to it.
> Otherwise
> the precision used to write out the errors is the same as for the model
> values.
So that means that a value of "1.1952008680668813, (+/- 0.0)" really
indicates an error identical to zero? I guess if the reduced chi
squares bottoms down to unity, there's not much else the fitter can
give us... But how can the fit be that perfect if there is noise in my
observed spectrum?
Cheers,
Matthijs
>
> Cheers,
>
> Peter.
>
> (BTW, I've updated the script as you suggested, this will be in the next
> release coming soon, thanks).
>
>
>> On Mon, Jan 3, 2011 at 1:54 PM, Matthijs H.D. van der Wiel
>> <[log in to unmask]> wrote:
>>>
>>> Thanks Malcolm, Peter,
>>> This script does exactly what I want.
>>>
>>> I am fitting two Gaussians. Judging from the result of the fit, I
>>> gather that the 'width' parameter refers to the mathematical sigma of
>>> the Gaussian function (i.e., I multiply it by 2.35 to get FWHM). It
>>> might be good to state the meaning of 'width' for the Gaussian first
>>> guess (and output) explicitly in the prologue documentation of the
>>> script.
>>>
>>> Another minor note about the documentation:
>>> Under "output files" it says that the fitted model parameters are
>>> descibed in "result.config" and "result.log", while the script in fact
>>> writes to files called "report.config" and "report.log".
>>>
>>> Cheers,
>>> Matthijs
>>>
>>>
>>> --
>>> M.H.D. van der Wiel
>>> Kapteyn Astronomical Institute, University of Groningen
>>> & SRON Netherlands Institute for Space Research
>>> [log in to unmask] // http://www.astro.rug.nl/~wiel/
>>> Kapteynborg, room 183 [Landleven 12]
>>> tel: +31 (0)50 363 4083
>>>
>>>
>>>
>>> On Sun, Jan 2, 2011 at 1:02 PM, Peter W. Draper <[log in to unmask]>
>>> wrote:
>>>>
>>>> On Fri, 31 Dec 2010, Malcolm J. Currie wrote:
>>>>
>>>>> As far as I know specification of blended fits is only available via
>>>>> the
>>>>> command-line tool $SPLAT_DIR/deblend and a text configuration file,
>>>>> rather than a graphical interface.
>>>>
>>>> Yes, that is still the case.
>>>>
>>>>> Read the prologue of that file for more details.
>>>>
>>>> Indeed,
>>>>
>>>> Cheers,
>>>>
>>>> Peter.
>>>>
>>>
>>
>
> --
> Peter W. Draper, http://astro.dur.ac.uk/~pdraper
>
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