[Ifeffit] Re: sigma squared

[Karla]

Yes, and when I regenerate the plot, a window pops up to show what range 
I picked, right?  This window does not intersect at 0 on the Xs I 
picked.  I believe the correct x values are written.
 
Matt Newville wrote:

>Karla,
>
>  
>
>>>I have a couple of questions.  First, in Artemis, when I click on
>>>the "x" buttons to select my k- and r-ranges, the window never seems
>>>to correspond to where I clicked.  Is this a bug?
>>>      
>>>
>>Probably not.  The default in Artemis is use a Kaiser-Bessel window.
>>The various strange words to describe FT windows ("Kaiser-Bessel",
>>"Hanning", "Welch", and so on) refer to different functional forms for
>>...
>>    
>>
>
>I don't understand "the window never seems to correspond to
>where I clicked".  What should happen is this (in order):
>  - you click on the [x] box to the right of a parameter
>  - you click on the plot window
>  - the 'x' (E, k, R) value of the point you clicked on 
>    gets written into the entry for the parameter value 
>    (to the left of the box).
>  - you re-generate the plot to have this selected value 
>    take effect.
>
>Is that not what happens?  Are you saying that the wrong 'x'
>value is getting written into the parameter entry or that the
>window looks different than you think it should?
>
>For the negative sigma2 values, I agree with Bruce: it's not a
>bug, exactly.  More generally, it's not trivial for the fitting
>procedure to know that some variables or even Path Parameters
>have "unreasonable values" unless a) the program enforces how
>you model the data (which leads to loss of flexibility) or b)  
>the user explicitly says what "reasonable values" are, either
>using rigid math expressions or the restraint mechanism.
>
>--Matt
>
>  
>
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