[xas_viewer] features requests on selecting E0

[maurov]

@newville I have a couple of features requests from our users at the beamline, regarding E0 selection:

• [ ] select E0 at a set fraction of the the edge step.
• [x] plot second derivative.
• [ ] select E0 at zero-crossing of the 2nd derivative.

I write down this here as a reminder.

[newville]

@maurov All fine suggestions. Will try those

[newville]

@maurov this is now fixed, almost ready to push out 0.9.55....

[maurov]

@newville thanks for working on these features. I see the plot of the second derivative, but I do not see in the GUI how to select E0 at a fraction of the edge step or at the zero-crossing of the 2nd derivative.

[newville]

@maurov yeah, sorry I should have commented here earlier: the second derivative was easy, "fraction of edge step" seemed harder -- but is still on the ToDo list. Basically, I felt like I needed to get 0.9.55 out sooner rather than later.

So, I would say let's leave this open as it is not complete. Yet.