Example STEM EDS of joint interface

[jorgenasorhaug]

STEM EDS data analysis. Element quantification and signal clustering.

Requirements

• Read the contributing guidelines.
• Fill out the template; it helps the review process and it is useful to summarise the PR.
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Description of the change

A few sentences and/or a bulleted list to describe and motivate the change:

• Provided an example notebook to show STEM EDS signal processing, element quantification and signal clustering.

Progress of the PR

• Change implemented (can be split into several points),
• docstring updated (if appropriate),
• update user guide (if appropriate),
• added tests,
• add a changelog entry in the upcoming_changes folder (see upcoming_changes/README.rst),
• Check formatting of the changelog entry (and eventual user guide changes) in the docs/readthedocs.org:exspy build of this PR (link in github checks)
• ready for review.

Minimal example of the bug fix or the new feature

import exspy
import numpy as np
s = exspy.signals.EELSSpectrum(np.arange(100).reshape(10,10))
# Your new feature...

[CSSFrancis]

@jorgenasorhaug This is a fantastic addition to the documentation! We should think about the best way to add this to exspy in a way that we can:

1. Test the jupyter notebook (so that it continues to work if something in hyperspy/exspy changes!)
2. Display the notebook as part of the docuementation --> We use nbsphinx to do this in pyxem along with some code for downloading notebooks.... This works most of the times as long as the notebooks are updated :)
3. Easily acess the data from zenodo --> we can just use pooch to get the dataset. It might be also useful to think about if the data is general enough that it could be stored as a exspy.data module similar to pyxem and kikchipy.

@ericpre Do you have any perference here?

[ericpre]

For now, the notebook should be added with the other notebooks at https://github.com/hyperspy/exspy-demos. Please make a pull request there and we will review it.

@CSSFrancis, at you said, it would be good to make these notebooks easier to go through and rendered from the documentation but let's keep for another PR! 😃

[jorgenasorhaug]

I made a new pull request with the demo provided in hyperspy/exspy-demos as requested (hyperspy/exspy-demos#7).