[Ifeffit] Importance and Edge Step

[Gerrit Schmithals]

Hello,

>Importance:
>  This number is used only in a merge and only when the "Weight by importance"   
>  button in the Merge menu is checked.  It's intention is to allow 
>  user-specified weights in a merge.  If you trust one data set twice as much 
>  as another, the more trusted one might be given an importance of 2 while the 
>  other is given an importance of 1.  This was in response to a feature 
>  request -- personally I am not clear how would know how to weight different
>  data sets. 
>
>  
>
Oh, that's why it is called 'importance'. I actually used it for a
different purpose: I have experimental data of an unknown sample but
suppose it contains iron and probably iron carbide. I loaded
experimental data for iron foil and iron carbide (I took the latter from
the Newville-database - thanks for that ressource!) and merged them in
chi(k). I used the 'importance'-factor for weighting the experimental
values to reflect different concentrations.

This should usually be done using Artemis - but I do not know if there
exist crystallographic data for iron carbide, so that was the only way
to simulate a mixture I could think of.

Actually the comparison of the merged dataset with my unknown sample was
not very good. Which might be explained by the fact I do not have a
mixture of these substances. Or is there anything fundamentally wrong
with what I was doing?

>Edge step:
> 
>This does not appear to be working, if I check "Fix Step", enter a value into the edge step window, and then recompute the background, the value of the edge step reverts back to the automatic value.
>
I can affirm that bug: the edge step is not fixed just by choosing the
'fix step'-box. Work around: first click on one of the arrow buttons
which will automatically enable 'fix step'. Then you can enter a value
for the edge step which will now be fixed correctly.

Cheers,
Gerrit